32 OSBORN. [Vol. XVIII. 



.006 mm. in diameter, and consist of a nuclear membrane, scattered 

 and indefinite chromatine in small grains, and a nucleolus. The' 

 nucleus nearly fills the cell and the cytoplasm is small in amount. 

 These cells bear a close resemblance in size, position and structure 

 of the primitive cells of the spermary. The center of this portion 

 of the ovary is occupied with a type of cell shown in Figs. 53 and 

 54, doubtless derived from cells of the sort just described, which 

 show different stages of mitotic division. In the center of the 

 ovary we find much larger cells (Fig. 55) with a nucleus of a 

 diameter of .01 mm., in which a distinct membrane encloses a 

 large nucleolus which is a center of a system of minute threads on 

 which minute grains of chromatine are arranged. These cells have 

 a large amount of cytoplasm of a fine-grained homogeneous tex- 

 ture completely filling the faint but definite cell membrane. These 

 cells are much crowded which results in the production of the 

 characteristic .wedge shape. They fill this region of the ovary com- 

 pletely, to the entire absence of the parietal cells of the deeper 

 portion of the organ. In the anterior part of the organ the cells 

 (Fig. 56) attain a size of .033 mm. The nucleus now is still larger 

 (.015 mm. in diam.) and the nucleolus is very large, .004 mm. 

 The granular chromatine is very scanty in amount. The cyto- 

 plasmic portion of the cell, unlike the preceding stage, is greatly 

 vacuolated. This condition does not appear to be artificial, since it 

 is found in specimens hardened in a great variety of reagents, 

 corrosive, picro-nitric and chrom-osmium-acetic. Cells of this sort 

 are seen in some of the sections in the act of descending into the 

 " fallopian tube " as Voeltzkow called the following upper part of 

 the oviduct in Aspidogastcr. As it is probably in the " tuba " that 

 fertilization takes place (vid. Stafford '96, p. 49) one would expect 

 that the maturation of the egg would occur in this part of the 

 ovary itself or in the tube leading to the upper part of the " tuba." 

 I have not, however, as yet been able to observe any ova in this 

 situation in .which there is any indication of nuclear activity. 



The position of the ovary in Cotylaspis is just the reverse of that 

 in Aspidogastcr, where the deeper portion is anterior and the part 

 next the " tuba " is posterior. This difference involves only the 

 ovary and the upper part of the tuba, which in Aspidogastcr is 

 suddently bent on itself in the middle, while in Cotylaspis it is 

 straight. 



