466 REPORT OF COMMISSIONER OF FISS AND FISHERIES. '[12] 



not broiiglit in contact with the mate spermatic fluid tbe outer pellicl^e 

 of germinal matter retained the disposition showu in Fig. 1, with its yi- 

 cluded vesicles, but as soon as tbc egg was fertilized, or shortly there- 

 after, the vesicles were seen to grow larger and less numerous, because 

 the clusters were coalescing and apparently being expelled from the 

 germinal matter. So great was the influence of the i^resence of sperqia- 

 tozoa that those eggs in contact with tliem began to change alniost'i^n- 

 mediately, wJiile unfertilized ova retained their vesiculAted germinal 

 layer unchanged £br four hoUjfs after their reuioval from, the ovaf y of 

 the parent fish. . , ' , , . ^.„ 



The disappearance, of the vesicles above described icas t7ierefore 'dk inaica- 

 Uon of the /act that impregnation had taketi place^ ^ . ^ r^^ 



Since the foregoing was written the writer has observed''' similar phe- 

 nomena in the oy<i of Tylosurus, Ulacate,am\ Cybimn, in all of which tile 

 development of the germinal disk is ejected by the aggregation pf 'the 

 germinal pellicle at one pole to form the .germinal disk. The satire Is 

 true of the eggs of the branch herring, Powo/o&?<s vernalis, iind the sljiitl. 

 The germinal pellicle is, moreover, part .and i)arcel of the intermediary 

 layer of Van Bumheke, couchejiccmatogene of Vogt, and parablast of 

 Klein; the germ di^kand tbe yelk hypoblast are both derived fi-oiii it, 

 as we shall learn farther on, Jt includes botb of the latter, and' the 

 names bestowed upon the cortical lay^r by diflerent embryologists siup- 

 ply serve to deno ruinate what, was at first a part of the germinal matter 

 pf the egg and afterw^ards becomes the envelope of the ye)k. ,_'. ' "^ 



Balbiani states that Agassi z and Burnett recognized evident ttaqj^s 

 of segmentation in the unimpregnated eggs of 'certain American tishes 

 of the cod family. As the \yriter has been unable to find the, original 

 of this statement, it will be of little use to discuss thp matter in the ab- 

 sence of all evidence to confirm the observatiou,!,ior,'as not even a gi^r- 

 minal disk was developed in unimpregnated eggs bf the cod. after iblir 

 •hours had elapsed, in impregnated ova it was appreciably developed 

 ,0116 and a half hours afterwards ; it follows that it is not probable ^hat 

 any true cleavage of the germinal disk of this spepies evqr takes' pliice 

 without the mfluence of the spermatic particle. , .. 



^ Tljatt|e, germinal dis^^^^ 



the spermatozoon In many otiier species there caunbt- however, be ilie 



slightest, doubt, I have witnessed this plienoniehou iii the eggsofdlii- 



^ Vostonia, Morone, Parcph ij^p^c^: i>nd Ccrataqanthun, while it is known to take 



^^l)lace in many other species investigated by European authors, but tljie 



disk appears in some cases at least to have been differentiated f)eipro 



it leaves the intraoyarjaii cavity, as in. some iSalmonid.a\ tor exaniplel^'. 



, In order to ascertain more defiuiteiy the natur<^ of the minute vesicfips 



inclosed in the germinal layer, a number of '\ihimpregnatcd ova were 



placed in dilute acetic acid, which had the efiect of freeing the bitter 



germinal pellicle froun, the yelk. , The pellicle w{ls then carefully removed, 

 and stained with hajmatoxylon anct mounted; the protpplasi^ iriterven- 



