366 LOUIS MAX HICKERNELL. 



of the chromatic material has collected close to the nuclear wall 

 and the central area shows a more or less clear condition. This 

 change in the position of the chromatic material in the nucleus 

 is not the only one incident to the drying process in the vitel- 

 larium or in the other organs as a comparison of the figures will 

 show, but it is by all means more frequent than the other changes. 



The condition of the ovary in the dried animal is best shown 

 in Fig. 21, Plate V. It will be remembered that the cytoplasm 

 of the undried ovary usually shows as a glassy, homogeneous 

 ground substance and that the nuclei appear as dense, spherical 

 bodies closely packed in this syncytial ovarian cytoplasm. In 

 the dried ovary the cytoplasm becomes more deeply staining 

 and assumes an appearance not unlike that of the vitellarium. 

 The nuclei become less dense and the chromatic material col- 

 lects in a peripheral ring as was described for the vitellarium 

 nucleus. 



In Fig. 21, Plate V., a trough-like depression is seen at the 

 margin of the vitellarium which lies nearest the integument. 

 This is caused by one of the band-like, circular muscles, which, 

 drying in the contracted condition, caused a deformation in the 

 vitellarium tissue which shows thus in longitudinal section. 



At this point it might be well to comment upon the fact that 

 many of the muscles in the rotifer body actually dry while con- 

 tracted. It would seem that when the normal moisture con- 

 tent was removed from a muscle that it would have a tendency 

 to relax and in this way cause the animal to become more loosely 

 folded during the later stages of drying. That this is not true is 

 evident from the figures and descriptions given. The rotifer 

 remains tightly contracted during the most complete conditions 

 of desiccation. 



This condition may be due to two factors. In the first place 

 the integument is the first structure to dry. The moisture 

 evaporates from the surface more quickly than from the internal 

 structures. This integument is chitinous in its outer layer but 

 is of such consistency that while moist it is very pliable. When 

 the moisture is removed, however, the cuticle becomes more 

 rigid. In this respect it might be likened to gelatin and such a 

 resemblance is indeed noticeable. Now with the withdrawal of 



