CYTOLOGICAL CHANGES ACCOMPANYING DESICCATION. 337 



packed together. Under conditions mentioned hereafter this 

 granular appearance may give place to a dense homogeneous 

 black ring (iron-haematoxylin preparations) staining exactly like 

 the normal karyosome. The changes in the cytoplasm, though 

 distinct, are much less marked than the nuclear changes. With 

 the withdrawal of water the cytoplasm increases in density and 

 loses the regular arrangement of its particles which is char- 

 acteristic of the normal vitellarium (Fig. 4). The yolk granules 

 become arranged irregularly or in small closely packed groups 

 as in Fig. 5. The drying process causes a loss of staining power 

 in the tissue. 



The shrinkage of the cytoplasmic portion of the tissues is well 

 demonstrated in the case of the hypodermis. Fig. I show as 

 section of this layer of the skin as it appears in the animal living 

 under normal conditions. In a section through the dried animal 

 (Fig. 2) it will be noticed that the hypodermal layer has shrunken 

 markedly, approaching its normal thickness only in those places 

 where the nuclei are located. The nuclei apparently do not 

 diminish in size and they cause a protuberance in the dried 

 hypodermis wherever they are found. The nuclear material is 

 redistributed in the same manner as was described for the vitel- 

 larium. 



This arrangement of the nuclear elements is found in prac- 

 tically all the tissues of the dried animals. A detailed description 

 of the changes in the other organs would be, for the most part, 

 mere repetition. 



As was mentioned above, the cilia in P. roseola are well de- 

 veloped, both in the head region and in the digestive tract. 

 It would seem that a fiber of such delicate texture as that of a 

 cilium would not long survive the effects of a removal of moisture. 

 Such, however, is not the case. Not only do the trochal cilia 

 escape serious injury by the desiccation process but the same is 

 also true of those in the digestive canal. Fig. 2 shows a section 

 cut through the infolded trochal discs of a dried animal. There 

 is no sign of any fusion or other abnormal condition of these 

 elements. Each cilium preserves its identity apparently as well 

 as would those of an animal living in a natural environment. 



The changes in cell structure attending recovery from desicca- 



