1893.] *^ [Hubbard. 



chromic-acetic. A few others in phitinum chloride and corrosive subli- 

 mate. Those killed in the two last mentioned were not very favorable for 

 the study of the yolk nucleus. Some of the ovaries were stained in tolo 

 by hfematoxylin. Others were stained on the slide by eosin. Tiiis is 

 an excellent stain for eggs near maturity. The former was the better for 

 younger eggs. After clearing with clove oil and infiltration in paraffin 

 they were cut and mounted in Canada Balsam. 



I made a number of experiments with dificrent staining media. Neither 

 mythyl green, mythyl violet, dahlia or safrinin sufficiently ditFerentiated 

 the tissues and the body I wished to trace. I found, however, that mythyl 

 violet did not stain anything in the ovary, but did stain the outside mus- 

 cular tissue and the spermatazoans contained in the ovary, the latter be- 

 ing stained a bright violet. Using alcoholic eosin and methyl violet as a 

 double stain rendered all the tissues red except the spermatozoons, which 

 were a bright violet. 



I have examined the ovaries of very small fish measuring 17 mm., 29 

 mm., 35 mm. and 40 mm. in length. In none of the largest eggs of these 

 did I find any trace of a yolk nucleus. In a fish 45 mm. long I found a 

 few. eggs which seemed to have this body, but not at all distinct, as the 

 ovary was not well preserved. The adult fish reaches a length 140 mm. 

 In a fish 70 mm. long I found this body quite distinct. So it must appear 

 in the egg when the fish is between 40 mm. and 70 mm. in length. But, 

 as I had no specimens between these two sizes, I cannot definitely de- 

 termine just when it appears in the egg. 



In tlie young, 40 mm. and less in length, the largest eggs measure 35 /u, 

 30 fx, 25 /I. In none of these eggs was the body visible in the proto- 

 plasm of the egg. But eggs about tlie same size as above found in an 

 ovary of an adult fish showed clearly the presence of this body. This 

 early stage was not seen in all the ovaries sectioned. The one in which 

 it was seen was taken October 21, killed in osmicchromic acetic, stained 

 in hsematoxylin, cleared with clove oil and mounted in Canada Balsam. 

 The smallest egg in which the yolk nucleus was observed was 20 /n in 

 diameter, i. e., it was smaller than the largest egg in the ovary of the 

 small fish 40 mm. in length, in which the yolk nucleus had not appeared. 

 In these eggs of the adult fish the protoplasm around one side of the nu- 

 cleus takes a deep stain. It appears as a crescent-shaped body, fitting 

 very closely to one side of the nut-leus and forming a kind of cap (Fig. 

 1, yk. nl.)- Anotheregg of the same measurement shows a little more 

 advanced stage. The body is more definite in shape, not of so pronounced 

 a crescent form and appears to have enlarged considerably (Fig. 2, yk. 

 nl.). The next important change is seen in a slightly larger egg, 25;/ in 

 diameter (Fig. 3, yk. nl.). Here tlie body has assumed an oval form 

 without any definite cell wall or hird outline. Although usually touch- 

 ing the nucleus it seems to have no further connection with it. In this 

 egg it is quite large, measuring 10 fi in minor axis and 12^ /i in major 

 axis. From this time the body seems to have severed its connection with 



