MUUSEM OF COMPARATIVE ZOOLOGY. 71 



He claimed for Cyprinus erythrophthalmus, Perca fluviatilis,and Acerina 

 vulgaris a velvety appearance of the external surface of this membrane 

 " as if beset with tufts " (Zotten *), which he ascribed to " very small cy- 

 lindrical projections or rods with rounded ends," — prolongations of the 

 vitelline membrane itself. Here again Miiller unfortunately confounded 

 the unlike conditions of different eggs. While his conclusions have been 

 confirmed in the case of Cyprinus erythrophthalmus, I know of only one 

 author whose observations give any evidence of the presence of such a 

 " pile " or velvety structure outside the zona in either of the other fishes 

 mentioned. Hoffmann ('81, pp. 19, 20, Taf. I. Figs. 9, 10), it is true, not 

 only figures an external layer of the zona in a nearly ripe egg of Perca, 

 which is thinner and much more sparsely striate than its inner layer, but 

 he also describes and figures an October egg as possessing outside the still 

 thin zona a layer of minute, close-set tubercular projections which " fully 

 correspond to the Zottchen of the Cyprinoids." I believe that Hoff- 

 mann has in some unaccountable way fallen into an error in this matter. 

 At least, no other observer has seen any trace of the structure which he 

 describes, and an examination of the eggs of our American perch in 

 October reveals nothing of the kind. I think the condition in Acerina 

 is probably similar to that in Perca, — certainly no one has shown the 

 presence of a " Zottchen " layer. That being the case, what was it 

 that Miiller mistook in Perca and Acerina for " Zottchen " 1 A state- 

 ment by Owsjannikow ('85, p. 18) makes me believe that Miiller may 

 have had under view the branching deep ends of the tubular structures 

 which according to Owsjannikow traverse the gelatinous envelope, and 

 which are left sticking in the pore-canals of the zona when the two 

 layers are artificially separated. It may be, however, that Miiller saw 

 the more conspicuously — but not, as Hoffmann makes it, more sparsely 

 — striated outer portion of the zona itself, in which event it might be 



1 Muller was not the first to see the appearance presented by these "Zotten," 

 nor even to suggest the name. Von Baer ('85, p. 7) had, twenty years before, 

 seen the same thing in species of carp. " Die aussere Eihaut ist aber nicht 

 ganz formlos und gleichartig in sich. Sie enthalt in den Karpfenarten, die ich zu 

 untersuchen Gelegenheit hatte, keine [should be kleine] dunkleren Vorragungen, die 

 ihr bei starker Vergrosserung ein zottiges Ansehen gaben." It is evident that Von 

 Baer confounded the radial " tubes " in the outer envelope of the perch egg with 

 these villi of the carps, for he adds : " Im Barsche ist diese Hiille noch sehr viel 

 dicker und man sieht, dass die dunklern Flecken, die hier lang und schmal sind, in 

 der aussersten Schicht sich befinden." One will find little occasion for surprise at 

 this parallelism, in view of the fact that some of the most recent observers, with 

 the best modern appliances at command, have arrived at a similar, though I believe 

 erroneous conclusion. 



