4GS M. Louise Xicliols. 



sule. Material, however, seems to have collected close to the wall 

 of the capsule. No ring is present at the distal end and the nucleus 

 is condensed, flattened and surrounded by the mitochondrial sub- 

 stance. Enclosed- in a vesicle just posterior to the middle-piece lies 

 a densely staining body, probably the distal centrosome. In Fig. 

 10 the inner tube is complete, a ring has appeared at the distal end 

 and the entire capsule has elongated. Cross sections (Figs. 9 a-b) 

 give some idea of the manner of formation of the tube, apparently 

 by a condensation of the capsular material which still remains 

 connected with the outer wall by delicate strands. 



Likewise in the development of the spermatid of Eupagurus longi- 

 carpus a few stages were studied. A "ISTebenkern" appears in the 

 youngest of them. It increases considerably in size as the nucleus 

 stains more deeply and Anally takes its position between the nucleus 

 and the tail-capsule as the middle-piece. A densely staining globule 

 appears at the distal end of the capsule similar to that of Hippa, 

 but much smaller. The smaller size of the spermatid of Eupagurus 

 at this stage is also noticeable and the more densely colorable nature 

 of the nucleus. (PL 3. E, 1-5.) 



Among the Carididae I examined only Palaemonetes. The cell 

 walls between adjacent spermatids break down and the nuclei lie in 

 a common cytoplasm. Three such nuclei are represented in Figs. 

 P, 1-3. PI. 3. In the first the chromatin appears finely granular 

 and the nuclear membrane is not sharply defined, the second is under- 

 going a process of degeneration and fragmentation, while the third 

 is developing normally. The nucleus has lost its finely granular 

 aspect and has become more or less opaque with a few "ill-defined 

 darker spots. A ring of cytoplasm has condensed about it (mito- 

 chondria) in which dark granules are scattered. In the next stage 

 (Fig. P, 4) a portion of the ring has differentiated into a tail, be- 

 tween which and the nucleus two large dark spheres have arisen. 

 Down the center of the tail also runs a slender dark filament. In 

 the mature spermatozoon usually but one of these spheres is dis- 

 coverable. In pole view (Fig. P, 6b) rays are seen to extend from 

 it to the nucleus. The nucleus is now lens-shaped, sometimes cup- 

 shaped. (Fig. P, 5, 6a.) 



