70 BULLETIN OF THE 



vitelline membrane. 1 Aubert describes the "shell" of the egg of Esox as 

 a transparent thin membrane, furnished with fine points, which closely 

 envelops the yolk. These points exhibit a great regularity of arrange- 

 ment, being placed at the intersection of symmetrical curved lines. 

 When the shell has lain some time in water, it separates in many places 

 into two membranes, of which the outer is very thin, finely granular, 

 and irregularly elevated, while the inner is thicker, uniform, and upon 

 sections exhibits fine radially placed streaks. 



I believe it is certain that the radial streaks described were due to 

 the pore-canals, although the author does not fully commit himself to 

 that view. " The spermatozoa are so large," he says, " that it would be 

 difficult for them to pass through the ' points ' of the shell, in case the 

 latter are regarded as the lumina of fine canals." 



Also Lereboullet ('54, pp. 240, 242, 245, 249) wrote concerning the 

 pike : " The ripe egg is surrounded by two membranes : the external is 

 pierced by microscopic tubes, which serve for the absorption of water, 

 and consequently for the respiration of the egg ; tne internal, applied 

 to the vitellus, is a simple, extremely thin and amorphous protecting 

 envelope." He also saw the pore-canals in the perch, and argued that 

 the expulsion of albuminous globules from the fertilized egg proved 

 the absence of a vitelline membrane at that time, and that it went to 

 confirm the opinion of those who regarded the chorion as produced by 

 the primitive vitelline membrane, which was itself detached from the 

 vitellus. 



Although J. Muller ('54) contributed much to the knowledge of the 

 egg membranes, especially of the perch, and was also the first to appre- 

 ciate the importance of the difference in origin between the egg-shell in 

 birds and what he called the " egg capsule " in fishes, he did not fully 

 comprehend the structure of what he called the "Dotterhaut" (zona). 



1 I cannot agree with His (73, p. 2, foot-note, compare also p. 14) in his criti- 

 cism of Aubert when he says: " Der Name Dotterhaut, welclien die friiheren 

 Schriftsteller fur eine besondere den Dotter unmittelbar umhiillende structurlose 

 Membran gebraucht haben, urird von H . Aubert (Beitrage, etc., 94) oaf die Eikapsel 

 nngewendet. Er spricht namlich bein Hecht-Ei von einer Trennung der Dotter- 

 haut [!] in zwei Schichten, eine iiussere diinne, fein granulirte und eine innere, 

 dieke, mit radiaren Streifen. Eine Begrundung seiner abweichenden Bezeich- 

 nungsweise giebt er nicht." 



Aubert says distinctly enough that it is the " Schale " which is divided into two 

 membranes ; and although he nowhere employs the word " Dotterhaut," there seems to 

 me no doubt that he has Dotterhaut in mind when he says : " Der Dotter wird 

 von einer sehr fein kornigen, sonst structurlosen Haut iiherzogen." His may have 

 been misled by the statement that "Die Schale etc. den Dotter eng umgibt." 



