86 BULLETIN OF THE 



rating the layers. The inner layer is composed of two parts, the outer 

 part being often striated concentrically. The membrane of the fully 

 ripe egg is different. Before contact with water the pore-canals of the 

 outer layer are not so easily distinguishable as in immature eggs, and in 

 this layer a great number of small lustrous spherules are now visible. 

 In eggs which have been in contact with sea-water the outer layer is 

 raised up from the inner, forming a viscid sheet 10-12 //, thick, which 

 causes the adhesion of the eggs. The outer portion of the inner layer 

 now exhibits a tendency to split into concentric layers, which obscures 

 the radial pores, although they are still visible in the deeper part of 

 this portion. 



It appears to me probable that the two portions of the inner layer 

 represent the whole of Kupffer's capsule, and that Hoffmann's outer 

 layer is the equivalent of Kupffer's viscid semifluid substance. In view 

 of the striate appearance of the outer layer described by Hoffmann, and 

 the greater coarseness of the striations as compared with the inner layer, 

 and also in view of its viscid nature, I am strongly inclined to believe 

 the outer layer will ultimately be shown to be equivalent to the villous 

 layer in other bony fishes. 



Two layers resembling those of the herring were also found in Creni- 

 labrus. Greater interest attaches, however, to the account of Leuciscus 

 rutilus, in which, as the author says, one again finds the two layers of 

 the zona radiata. But in the next sentence he shows that he does not 

 distinguish sharply between zona and villous layer : " The outer layer 

 here forms the well known Zbttchenschicht." The villi are club-shaped, 

 close set, and clothe the zona as a uniform layer, with the exception of 

 the place where the micropyle is situated. In the extent of their distri- 

 bution, therefore, the villi in Leuciscus differ from those of Lepidosteus, 

 — which, though shorter, are not wanting in the periphery of the micro- 

 pyle, — and also present a condition which is the complement of that 

 exhibited by Heliasis, Gobius, etc., in which villous structures are 

 restricted to the region of the micropyle. 



Hoffmann arrives at these general conclusions : In adhesive eggs the 

 zona radiata consists of two layers, of which the outer effects the ad- 

 hesion. The latter may form a part of the whole zona, or may exist in 

 the form of villi over the whole surface, or of long filaments limited to the 

 micropylar region. " But whatever form this outer layer may assume, 

 it always has a like origin with the rest of the zona ; it is nothing else 

 than a part of the zona itself, which sooner or later undergoes peculiar 

 metamorphoses." Hoffmann recognizes the difficulty of determining how 



