714 PROCEEDINGS OF THE ACADEMY OF [DcC. , 



than wide, and is slightly broader at its posterior end. It stains 

 deep black with iron-ha3matox3'lin, and blue with hieraatoxylin-eosin. 

 In some iron-hsematoxylin preparations that had been strongly de- 

 stained, the head appeared ashy gray with a minute black point at 

 the tip, fig. 58. The middle piece, m.b., is a four-lobed etructure. 

 In fig. 59 there is a middle piece that has been detached from a 

 spermatozoan and which resembles four small spheres. In side view 

 only two of the lobes are seen. The middle piece stains black with 

 iron-hfematoxylin, and red with hsematoxylin-eosin. The tail is a 

 slender filament, in which no structure could be made out, many 

 times longer than the head. 



The Ovary. — The wall of the ovary, like that of the testis, is a 

 flattened epithelium, fig. 54, Gon. W. 



No ovarian duct has been found, although several specimens of 

 different ages have been examined. It is possible that a duct may 

 form in an older stage than those studied, but it seems more prob- 

 able that the eggs are discharged by rupture of the wall. The 

 latter view is supported by the fact of the difficulty in keeping 

 the body wall intact while studying living females with large 

 ova. When a perfect specimen was placed on a slide with sea 

 water and covered, a method that was repeatedly used without 

 difficulty for males, and for females with smaller ova, the posterior 

 part of the body would almost invariably fragment. It was also 

 difficult to fix and harden a mature female without rupturing the 

 body wall. No especial importance was attached to these facts at 

 the time, but since finding from the study of sections that there is 

 no preformed ovarian duct, I am inclined to believe that the 

 fragmentation observed in the female specimens w^as caused by the 

 rupture of the body wall above the gonads, the break then extend- 

 ing farther around the body wall. 



Closely pressed against the wall of the ovary and attached to it 

 by their broad bases are the youngest egg cells." Fig. 54 is a cross 

 section of a portion of the wall of one of the youngest ovaries. 

 Although most of the smallest ova are distinct cells, here and there 

 several are seen, so close together that their boundaries cannot be 

 distinguished, and it is therefore probable that the ova arise from a 



'"As all the material exainineil was quite advanced in age, I liave had no 

 opportunity to study the youngest stages of the ova, so that therefore the 

 cells that are here describe! as the youngest are probably well on in their 

 development. 



