596 SHEINA MARSHALL 



fig. 1, e), and the whole was separated as a double Hydra. 

 Unfortunately this specimen died before reproducing itself 

 further. It should be noted that the mode of origin of the 

 second half of the compound is distinctly abnormal. 



Leiber (8) reports a case in which one component of a 

 double Hydra, just before the division had reached the 

 foot and the two were about to separate, itself divided again 

 at the hypostome. It died before further observations could 

 be made. These cases indicate that a tendency towards 

 doubleness may be inherent in some Hydra stocks. From 

 the infrequency and origin of these abnormalities and the 

 frequent death of the compounds, it does not seem probable 

 that longitudinal fission is a normal method of reproduction. 



I have seen transverse fission take place only in obviously 

 unhealthy specimens. 



Hydras are sometimes found in which two or more tentacles 

 are in process of fusion from the base upwards. This seems to 

 be a method of regulating the number of tentacles to the size 

 of the Hydra, for it is found chiefly in animals which are 

 decreasing in size, or in those which have an exceptionally 

 large number of tentacles for their size. The commonest 

 numbers of tentacles were five, six, or seven, but some 

 specimens showed as many as ten. 



The appearance of an animal undergoing ' depression ' has 

 been so often described that it is unnecessary to do so here. 

 In the early stages the Hydra may take on an appearance 

 very different from its usual, the differences being sometimes 

 those described as characteristic for another species. 



For several months the Hydras I had were overrun with 

 Kerona and Trichodina, but they seemed none the 

 worse for it. This is contrary to the observations of P. Schulze 

 (9), who states that Kerona caused depression in his 

 animals. 



Feeding. 



The Hydras were usually fed on a culture of Daphnia, 

 but were occasionally given Cyclops, Cypris, or small 



