364 LOUIS MAX HICKERXELL. 



at room temperature and then kept in an evacuated calcium 

 chloride desiccator for eighteen days. At the end of this time 

 it was fixed and sectioned. It will be observed that the cilia 

 still show as individual fibers and have not fused into a homo- 

 geneous mass as some authors assert must be the case when all 

 moisture is removed. There is no sign of fusion or other ab- 

 normal condition in these elements. Each cilium preserves its 

 identity as w T ell as would those of an animal living in its natural 

 environment. 



Of especial interest is the structure of the integument in the 

 dried state. It has been asserted, and for some time quite 

 generally believed, that just before actual drying takes place 

 the rotifer secretes a jelly-like capsule through pores in the 

 skin and this capsule hardens to make a water-proof cyst which 

 remains during the dry season and is dissolved again upon the 

 addition of water. Janson ('93) thinks it is not unreasonable 

 to suppose that a gelatinous covering is secreted. He reasons 

 that since the pedal glands (which are undoubtedly derived 

 from the hypodermis) are ^known to secrete a sticky substance 

 and since the tube-dwelling forms secrete a slime from their 

 skins which helps to make the tube, then the forms which survive 

 desiccation might easily do the same. He admits, however, 

 that he has not found the actual secreting tissues. 



Jacobs ('09) found, as a result of staining reactions with 

 methylene blue, that the integument in the trunk is undoubtedly 

 different in its chemical nature from that of the head and foot. 

 He says: "The fact that that part of the cuticle which alone is 

 exposed at the time of drying should be of a different nature 

 from the remainder is probably significant." Jacobs is con- 

 vinced that no water-proof cyst is secreted and he suggests that 

 the thickened integument of the trunk region may be a means 

 of preventing a too rapid evaporation as dryness comes on. 



While I have no cytological evidence to show that the sug- 

 gestion of Jacobs is correct or incorrect, certain it is that there 

 is no thickening by a secretion or otherwise of the integument in 

 the dried condition. Fig. 16 shows that instead of the integu- 

 ment being thicker it is actually much thinner than it w T as in the 

 undried condition. The cuticle shows no great change in thick- 



