[^1 ] EMBRYpaRA.PHy OF; OS^SgCjlIfS ;JF;ISHE3. ,,,,.,;. 475, 



reception of the spermatozoon, such as has been 4esaiihed by Kupffer 

 aqtti Beuecke iu the egg- of the hiu^prey. This structure is rei)reseiited 

 in Fig. 7, PI. I, at i)p. iu an egg of the cod, in which tlie formation 

 of the germinal disk has not yet been .completed. Eepeated_ observa- 

 tion convinced me that I was not looking g.t an accideutal feature, but 

 that it was constant during this and somewhat l^ter stages of develop- 

 inent antecedent to segmQutatipn. The actual ingress of the spermato-i 

 zopivjnto theowm Hiave nevec witn<?ssed, althpugh, the cod's egg is. 

 one of the best adapted of all fisii ova tor tliis purpose on account of 

 its transparency and small.size. If Fol's conii)vpssi;>r is used^ e^perii;newt.s > 

 rn^y b^ ypry readily carrijecl pi^ti i^l^d^^, t,h^ inicrpscQpe, a^d if the upi>ep , 

 and lower plates of the compressor are kei)t far enough apart so as just 

 to allow the eggs to remain free and mobile within a few drops of water,, 

 encircled by a ring of block tin or iiard _rubbeJ|, (^l^inped J[^y,tl3ie:CQV)^>.j 

 the eggs will always iUTange themselves in one position, with the germ- 

 inal disk downwards and the yelk uppermost. This peculiarity enables, 

 one to see only the lower face of the disk throngli,th§. large transpa??ent. 

 yelk above it when the tube of the microscope is placed vertically, or 

 its edge, or in optic section, wiien the tube of the microscope is placed 

 horizontally, with the stage and conipressor upright. Tp jsee the u>pper, 

 surface of the germinal disk of tbe live. egg it is wpst convenient, in 

 fact necessary, to have an inyertiiig prism attacljied., to the microscope,; 

 into the mounting of which the objectives may be screwed, so as to vievt;. 

 the eggs from below. Nachet's imxj;ted microscopc^j used inchemic:^!; 

 investigations, would answer well for this purpose. The .sketches which . 

 I have made were obtained from living <^.ggs treated in this way, withr 

 ont cpnipressipu while ;Co,nfined,withiir .the area of ^a h;i|xl rubber. pr; 

 mpt^al J" JBgji wJiich §§^y(^4i itOyhoId tl>.<^i W.at^n and eggs in placp i whi^n ,the[ 

 cover of the compressor was screwed down. Attempts made to wit- 

 ness the entrance of the sperm atpzoa by the help of the above described 

 appafxT-.t^ls^ using ,Yejry -dilute jni;:^tgr€is of milt.wtth: water, were not 

 successful. The proper mode of procedure, in order to demoustrate the 

 changes by histological methods, would be to take a batch of ova fresh 

 from the pvavy and divide thein iiit,p twq lots.; Ijnpregnate the one Ipt? 

 and allow the other to remain uuiuipregiiated. Then take of both a, 

 series of specimens at intervals of two or three minutes and place them 

 in adilute chromic acid solution to tix the nuclear and other protopla,ST. 

 mic changes, so as to afterwards facilitate staiiiing au4 the preparatlpn, 

 of sections, and the satisfactory studj' of all the changes which the 

 nuclear matter of the: germ has undergone until the time of the first 

 segmentation. A similar semes, plithe .iinimpregiiated qya would, fhrowi 

 some light upon the history pi,, 1^Ji§ .pypcess; 0;f , tlie. migratjon of, tljef 

 luicleus from the center of the egg^ if taken in connecfon with the 

 investigation of the mature and functionally active ovary with its pro- 

 ducts ill' di tf^reht conditions of rnatu ri ty . 

 The complete disappea^-ance of tlip..; ge^fiiW.H(aitiy,e^!^^ 



