We may give a brief account of the formation of the sexual cells in Selaginella. The first stages in the appearance of microsporangia and macrosporangia are identical. Later on in the one case each of the spore mother-cells breaks up into four microspores, in the other case only one mother-cell breaks up into four macrospores, the others disappear. On germination the macrospore becomes a fairly large prothallus with several archegonia: the microspore forms only one cell as the representative of the prothallus, the rest of the structure becoming the antheridium.

In Phanerogams (flowering plants) a drop of water is no longer necessary for fertilization. The spermatozoon reaches the ovum, not by swimming movements, but by a kind of growth. This difference has resulted in profound modifications. Fertilization may occur in the air, and it is no longer necessary for the macrospore to become detached it remains fixed on the individual from which it arose and there proceeds to develop. In the Gymnosperms the archegonia are fully formed in a prothallus of considerable size, but the Angiosperms which are more specialized, retain only traces of these structures. The microspores

(pollen grains) exactly as in Selaginella are produced in great numbers, but when they leave the parent plant they develop only if they reach suitable conditions. In germination there is shut off, as in Selaginella, a single cell to represent the

prothallus; later on in a few Gymnosperms it undergoes a few divisions representing the formation of the antheridium. In Angiosperms the reduction has proceeded further, and each pollen grain besides the prothallus cell produces only one or at most two reproductive nuclei. In all Phanerogams the reproductive nucleus reaches the ovum by being carried in a long tube which grows out from the pollen grain at the expense of nutriment derived from the female tissues.

Thus, the prothallus may be traced through marked stages of reduction from the condition in ferns, through Selaginella to Gymnosperms and higher flowering plants. But these phases of reduction are by no means to be regarded as repetitions of ancestral conditions.

In conclusion, it is plain that we cannot assert as a general law, that degeneration retraces the steps of evolution. In the vegetable kingdom no facts support such a conclusion. In certain special cases in the animal kingdom, the most recently developed structures are the first to disappear when atrophy sets in, but this proves no more than that these particular structures happened to be less stable, and to offer less resistance. It is quite impossible to make such facts support the generally held view, that degeneration is a kind of inverse of evolution.

It is very seldom that a living apparatus with complex functions loses all of them, but usually

preserves one or other; for instance, the leaves of parasitic flowering plants continue to serve as protectors of the buds, and degeneration does not affect the part that has remained functional. It is highly probable that the original function of leaves was assimilative rather than protective, and yet here it is the later function that is retained.

Even when all function is lost, and the whole structure degenerates, there is no reason why the degeneration should retrace the evolution. In the case of the atrophy of an organ in an individual especially in such pathological instances as those mentioned by Ribot, it may be that the latest formed parts are the most fragile, and the most ready to disappear; but the path of atrophy is quite different in the case of the gradual reduction of an organ in a species. When an organ becomes useless to a species, as in the case of the eyes of deep-sea Crustacea, the only thing that matters to the species is that it may be got rid of. Any individual variation tending towards reduction will be of advantage, and may be retained by natural selection. There is no reason to suppose that such individual variations appear in any inverse order; in fact we do not know that the appearance of variations follows any law at all. Perhaps the apparent inverse order of the degeneration of the pineal eye in lizards may be explained from the fact that the most recently acquired characters are frequently the most variable.

However, even when the most recent organs disappear first, we cannot speak safely of a law of degeneration inverse to evolution. In the actual evolution of many organs, parts have appeared and then completely disappeared. If degeneration were a true inverse of evolution, it would be necessary that such lost parts should reappear only to disappear again. Such observations apply both to ontogeny and phylogeny.

CHAPTER II

THE PATH OF DEGENERATION IN SOCIOLOGY

§ 1. Investigation of facts.

WE have now to see if degenerative evolution in social matters retraces the steps of progressive evolution.

In the first place the question cannot be even entertained with regard to some cases, and this for a general reason which will be dealt with later on.

When a complex institution-such as a commercial society or an administrative organizationbecomes useless and ceases to be functional, it usually disappears either by voluntary dissolution or else it is legally suppressed. In either case there is no slow retrogressive degeneration retracing inversely the steps of progress, for all the parts cease to

exist simultaneously. If certain parts of the suppressed institution are allowed to persist, these are by no means necessarily the oldest parts, but quite the contrary.

When, for instance, the Provincial States of Dauphiny and Normandy were suppressed by the French monarchy, only the titles with their corresponding emoluments were allowed to remain, and they were obviously of more recent origin than the States themselves.

It must be borne in mind that all the parts of an institution rarely become simultaneously useless and non-functional. Those which retain their utility longest are by no means always the most ancient in origin.

English sheriffs have gradually become of less and less functional importance, and now fulfil no other role than that of presiding over elections and accompanying the judges when on circuit. Both of these functions have been acquired recently compared with all those which the sheriff discharged in the days when the care and protection of the whole county practically devolved upon him.

The question then of the pathway of degeneration only arises in those cases where the same cause of dissolution simultaneously affects all parts of the institution, and where, without sudden interruption, degeneration is effected slowly but surely through many successive stages. This, of course, happens in the degenerative evolution of individual