ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 73 



The j)lienomena of senile degeneration are very interesting ; tbe first 

 external sign is a reduction in size ; StylomjcMa pustulata, for example, 

 being in the normal state 160 /x, gradually descends to 45 and 

 even 40 fx. In addition to this diminution in size there is, later on, a 

 loss of various organs, until, at last, we get formless abortions incapable 

 of living and reproducing themselves. 



The degradation of the nuclear apparatus has a somewhat different 

 history, according to the species; in StylonycMa jpustulata and Onycho- 

 dromus grandis it is manifested early by the partial and then complete 

 atrophy of the micronucleus ; later on, the nucleus itself becomes 

 affected, the chromatin gradually disappearing altogether. While these 

 are the morphological phenomena, the physiological are no less im- 

 portant, for the organism gradually becomes weaker, and there is a 

 " surexcitation sexuelle." Owing to the loss of the micronuclei conju- 

 gation is fatally sterile, and the conjugated forms die. From these 

 observations it may be concluded that the micronucleus is the essential 

 organ of sexuality in the Microzoa, and that it plays no active part in 

 phenomena which are purely vegetative. 



The forms undergoing senile degeneration may be said to have an 

 inevitable death before them ; they still live an individual life, but they 

 are dead to the life of the species. Notwithstanding this the sexual 

 element is not yet completely destroyed, but, in place of contributing to 

 the regeneration and preservation of the species, it accelerates the de- 

 struction and disappearance of these atrophied generations. With this 

 sexual atrophy there is also degeneration of other parts. The nucleus, 

 the regulator of the vegetative functions, becomes little by little dis- 

 organized, nutrient changes get gradually feebler, tlie general energy of 

 the organism diminishes, and the size becomes reduced. This senile 

 decay ends in death. 



It is clear that these considerations are by no means in accord with 

 the views of Weismann, which the author next proceeds to consider, 

 remarking by the way that the theory of the potential immortality of 

 Protozoa was first broached by Ehrenberg. M. Maupas regards Weis- 

 mann's theory as resting on the two axioms, that the Monoplastids know 

 nothing of physiological waste, and that their development by fissiparous 

 division is, consequently, the absolute equivalent of all the generations 

 which have arisen from a single progenitor. The first is regarded as 

 being completely false, the second as partly false and partly true. 

 Weismann does not appear to have sufficiently distinguished between 

 the superficial lesions from which all living beings may suffer, and the 

 more deeply seated retrogressive changes which are caused by senescence. 

 Like multicellular animals, the unicellular do suffer loss, and that 

 loss becomes intensified with successive generations The whole theory 

 of Weismann is an a priori one, and has no base in fact, while M. Maupas 

 thinks that the facts which he has observed contradict it. 



M. Minot appears to be right in discriminating between the various 

 kinds of individuality, and if the German naturalist had reflected on 

 them he would have immediately comprehended " toute I'inanite de sa 

 theorie de I'immortalite des Protozoaires," or, at least, he would have 

 seen its difficulties and would have hesitated to publish it. 



Believing that all organisms are fated to suffer senile decay, M. 

 Maupas refuses to accept Weismann's further hypothesis that death is 

 peculiar to the Metazoa, and has been brought about by some selective 

 action. 



