BDELLOID ROTIFER, (ALUMNA VESICULARIS. 261 



The toes were not clearly seen. They were rarely and only 

 momentarily displayed. From the few glimpses I got I do not 

 think they were symbiotic, but this is the one important point 

 which was not satisfactorily made out. The jaws have not the 

 broad border which I find in all the recognised symbiotic 

 species. 



The symbiotic foot, in which the toes are united to form a 

 perforated disc, is unmistakable in those species where it reaches 

 its fullest development, e.g. C. russeola and C. scarlatina ; in some 

 others it is rather obscure. 



Recently I have been able to watch C. scarlatina hatch out 

 from the egg. In the newly hatched young three toes could be 

 traced. The two lobes of the disc of the ad alt are probablv 

 reminiscent of the two principal (ventral) toes. Zelinka 

 himself figures C. symbiotica with two distinct toes, and I 

 have often seen it with three, in this case also probably 

 newly hatched. 



Of the habits of this new species there is nothing important to 

 tell. It creeps steadily and feeds sedately, like C. quadricor- 

 nifera. Only one of the three examples found was ready to feed. 

 From the others I was able to confirm the observations of the 

 teeth, tags, spurs, and foot-bosses. 



The yolk-mass had the usual eight nuclei ; no egg or foetus was 

 seen. The species is so well characterised that there is no other 

 with which it need be minutely compared to prevent confusion. 

 In the genus Callidina a higher tooth-formula than 3/3 is only 

 found among the pellet-makers and the symbiotic species. C. 

 vesictdaris has no affinity with the former group, in which 

 numerous teeth is the rule. From the known species of the 

 symbiotic group it is distinguished by the processes on the foot 

 and by the bladder-like vibratile tags. 



It seems to me to have most affinity with C. quadricornife/ra 

 and 0. habita, but even from these it is widely separated by 

 the characters of the teeth and the tags. 



