428 NOTES. 



particularly difficult to rear and which can even easily be measured ; 

 systematically conducted experiments on them would undoubtedly 

 yield .very pleasing and valuable results. Brauer's researches on the 

 Phyllcpoda afford a striking proof of this. He found that individuals 

 of a species of Chiroceplialus lived for weeks in a temperature of 19 C., 

 but never attained sexual maturity ; but they acquired sexual functions 

 within two days when exposed to a temperature below 11 C. The 

 eggs of a species of Branchipus could not be induced to develope 

 until after he had strewn them on slowly melting ice broken into 

 small fragments. It is much to be regretted that Brauer has given no 

 exact curves of temperature for the different species he reared ; but 

 even as it is, it would seem that we may infer from his remarks that the 

 optima of temperature are often very different for quite nearly related 

 forms. 



Note 42, page 120. With reference to these animals I must refer 

 the reader to Schmarda's list (Tkier$6O$faphie). The highest degree 

 of temperature hitherto observed as endurable by any fully grown 

 animal without inconvenience of any kind is 75 C. ; in Sparus D<:s- 

 fontaincsii in the hot springs of Tozer and Cafra in Tunis. Plateau's 

 observations (IfttcftcrcJiesjiJtysico-chimiqucs sur les Articulcs aquatiqnes, 

 2me partie, Bruxelles, 1872) only appear to contradict this ; for he 

 only experimented on such animals as live in cold water or thermal 

 springs of moderate heat. There is even a certain contradiction 

 between the results of his experiments and the facts he himself records 

 as to the existence of animals in these thermal springs. These springs 

 have, according to Plateau's list, a temperature corresponding exactly 

 to the maximum which can be generally endured by such animals ; 

 thus, if we regard his experiments as conclusive, they would live and 

 propagate in a temperature which, being indicated by the extreme limit 

 of the curve constructed to show their power of living, could not 

 therefore be regarded as actually favourable to them. However, the 

 experiments themselves were not conducted on a conclusive plan, for 

 the gradual cooling of the water was not prevented, nor were the 

 investigations carried on for a sufficiently prolonged period. But we 

 must not be led to confound with these certain well-known cnses of 

 great resistance to extreme heat exhibited by the eggs of the lower 

 animals, Insects, Rotatoria, Nematoda, &c., or by the capsuled Infusoria, 

 or by certain larvfe. It would seem as though these were thrown into 

 a state of latent vitality exactly as under conditions of extreme cold 

 during which their vital functions remained inactive ; while in the 

 animals living in hot springs exactly the same processes of assimilation 

 must take place as in those living in colder water. An experimental 

 investigation on an extensive scale of the power of resistance to high 

 temperature in the eggs or germs of the lower animals would certainly 

 amply repay the trouble. Brauer states that the eggs of Apus cancri- 



