480 MONTGOMERY. [Vol. XV. 



the periphery of the cell, so that the nucleolus is surrounded 

 by a clear space. These nuclei thus offer a suggestive object 

 lesson, to teach how careful one must be in the determination 

 of the form of delicate cellular structures by the study of 

 preserved material. 



Cells which are isolated have a spherical form ; those grouped 

 together are polygonal, owing to their mutual pressure (Figs. 

 99 and loi). A cell membrane is present. The cytoplasm is 

 for the most part finely granular ; portions of it, however, are 

 always more dense and stain more deeply than the former 

 portion ; there are great individual differences in different cells 

 (Figs. 100 and 102). Often the cytoplasm is more or less vacuo- 

 lar or a clear space may partially surround the nucleus and 

 a similar space be present between the cytoplasm and the cell 

 membrane, this space being transversed by a few radiating 

 fibers. Such spaces are best shown after the action of the 

 fluid of Hermann ; they are seldom to be seen after fixation in 

 picro-nitro-osmic acid ; but whether a coarse alveolar layer of 

 cytoplasm at the periphery of the cell be normal or be an arte- 

 fact, there are certainly marked differences in the structure of 

 the cytoplasm in neighboring cells, and these differences might 

 be regarded as the morphological changes corresponding to 

 functional phases in the cells. Cases of degenerating cells are 

 numerous, and may be recognized by their faint staining 

 properties and by their granular appearance. 



18. Giant Cells of Doto. 



(Plate 30.) 



(These enormous cells, which are the largest cells in the 

 body, not excepting the ova, lie at the anterior part of the 

 body just behind the head region and are closely apposed to 

 the folds of the nidamental gland. They do not produce a 

 closed mantle on the outer surface of this gland, but either are 

 isolated or occur in small groups of from two to four cells 

 each. In each individual their number appears to be about 

 thirty or forty. These cells do not seem to have any open 

 communication with the neighboring tissues, and I cannot 



