MUSEUM OF COMPARATIVE ZOOLOGY. 233 



four parts : two envelopes, an albuminous liquid, and a cicatricula. The 

 exterior mucous envelope, which is quite thick and resistant, is distin- 

 guished by a sort of loose network composed of very delicate fibres. 

 The interior envelope, of extreme thinness, hyaline, and likewise fur- 

 nished with a fibrous network, contains the albuminous liquor and the 

 cicatricula. The eggs of Limax rufus appear entirely like those of 

 Limax flavus. 



The figure given by Turpin is not such as to aid materially in under- 

 standing the structure. His exterior envelope includes both the exter- 

 nal stratified and the homogeneous layers, while his internal envelope 

 is the membrana albuminis, whose wrinkles were probably mistaken for a 

 fibrous network. The cicatricula is the yolk. . 



The description given three years later by J. L. M. Laurent of the 

 eggs of Limax flavus and of those of " Limace rouge," differs from that 

 of Turpin in only two or three points."^ Passing from without inward, 

 Laurent ('35^ p. 249) found in succession : — 



L A mucoso-corneous shell, evidently formed of concentric layers. 



2. An internal membrane. 



3. Two albuminous layers, the more liquid enveloping the denser 

 one. 



4. A very small vitellus, whose color, a slightly yellowish gray, varies 

 with the incidence of the light. 



No other author, so far as I know, has observed any differentiation of 

 the albumen into a denser and a more fluid portion. His " internal 

 membrane" doubtless corresponds to the memh. albuminis, and his 

 "shell," the concentric layers of which are first mentioned by this 

 author, embraces, like that of Turpin, the homogeneous as well as the 

 stratified portions. In a subsequent paper, accompanied by a plate, this 

 author ('38, pp. 155, 333, and PI. 3) states that between the corne- 

 ous shell and the internal membrane there is a clear space, which is 

 traversed by fibrillse (which in his Fig. 1 show a reticulated arrange- 

 ment) joining these two structures. A transparent, watery fluid may 

 accumulate in this clear space. It probably corresponds with the 

 viscid, unstratified shell layer of later observers. It is possible that 

 Turpin saw some such network of fibrillse, and hence ascribed to the 

 whole of the outer thick envelope this structure. I do not find it men- 

 tioned by subsequent observers, nor have I seen any such peculiarity 

 myself. 



* The eggs of L. flavus are united in a chaplet ; those of " Limace rouge " are 

 smaller and isolated. 



