DESICCATION IN PHILODINA ROSEOLA. 353 



in the region of the boundary between the "blasendarm" and 

 contractile bladder. The posterior strand looks as if it might 

 act as an oviduct but I have never seen an egg or an embryo 

 passing through it. This fact, together with observations of 

 other authors who have seen embryos of Philodina liberated 

 from the mother by a rupture of the body wall, makes it seem 

 certain that if this structure ever did function as an oviduct it 

 is now only rudimentary. The vitellarium contains eight large 

 nuclei arranged in a row. This number may vary but this is 

 not usually the case. 



The lateral excretory canals run posteriorly through the 

 trunk and very close to the vitellaria. They are minute, thread- 

 like structures having flame cells connected to them at intervals. 

 In P. roseola I have never observed more than five of these flame 

 cells on each side. The canals empty into the contractile bladder 

 as was described above. 



The rectum is a narrow tube leading posteriorly from the con- 

 tractile bladder and terminating dorsally in the anus (Fig. I, an.} 

 at the posterior border of the second foot segment. 



The foot contains the glands which secrete a sticky substance 

 which enables the animal to fix itself during its crawling move- 

 ments. These glands are oval in outline, are uninuclear and 

 empty by means of ducts at the base of the toes. When the 

 animal is folded up these glands become packed closely about 

 the "blasendarm." When the rotifer stretches out they occupy 

 places in the four posterior foot segments. There are four toes 

 on the tip of the foot. These aid in fixing the animal during 

 feeding movements. 



B. The Active, Free-swimming Animal. P. roseola in its be- 

 havior shows no great difference from most of the other Philo- 

 dinidae. Zelinka ('86) and Janson ('93) have described the 

 movements of the philodinids in general terms while Jacobs 

 ('09) has given an account of P. roseola both under ordinary con- 

 ditions and at the onset of desiccation. I have given the be- 

 havior of P. roseola much attention during the course of this 

 work and am able to confirm Jacobs in all essential respects. 



Two methods of locomotion are employed, viz., swimming by 

 means of the trochal cilia and creeping by the alternate use of 



