SCHALENDRUSENKOMPLEX BEI CEPHALOPODEN 



223 



coquilliers ne permet pas de distinguer l'épithélium primaire de l'épithélium 

 secondaire. 



— Les aires épithéliales responsables de la formation des différentes parties 

 de la coquille présentent une différenciation typique pour chaque espèce (pp. 193, 

 203, 214). 



10.3. SUMMARY 



— The histological and morphological development of the shell gland 

 complex of Sepia, Loligo and Octopus is described and compared. 



— The éléments of the shell of the three investigated species serve as an 

 attachment for the retractor muscles of the head and the funnel. This can be seen 

 in the médium embryonic stages. From the morphological point of view the Sepia 

 shell is able to exécute its hydrostatic function beyond Naef's stage XVI. 



— The development of the shell gland of Sepia, Loligo and the Sepiolids 

 coincides in fundamental points such as periods of growth of the anlage, stages 

 of initiating invagination, occlusion of the shell sac and attaining of the situation 

 which is typical for the end of the embryonic period. The primary and secondary 

 epithelium can be distinguished by reason of their characteristic development. 



— The rudiment of the shell gland of Octopus appears in an earlier stage 

 (IV) than that of Sepia and Loligo. Also the fusion of the edges of the shell gland 

 pore takes place earlier (st. VIII). But the situation which is typical for the end 

 of the embryonic period is achieved at nearly the same stage as in Sepia and 

 Loligo. Because of the spécial shape and the histological uniformity of both halves 

 of the shell sac it is impossible to distinguish between a primary and a secondary 

 epithelium. 



— The epithelial areas responsible for the formation of the différent parts 

 of the shells are typically developed in every species (see pages 193 ff, 203 ff, 214 ff). 



11. LITERATUR 



Appellôf, a. 1892. Die Schalen von Sepia, Spinila und Naiitilus. Studien Uber den Baii 

 und das Wachstum. K. svenska Vetens. Akad. Handl. 25: 1-106. 



— 1898. Uber das Vorkommen innerer Schalen bei den achtarmigen Cephalopoden 



( Octopoda) . Bergens Mus. Aarbog 12: 4-15. 

 Arnold, J. M, 1965. The inductive rôle of the yolk epithelium in the development of the 



squid, Loligo pealii (Le sueur). Biol. Bull. 129: 72-78. 

 Bather, F. A. 1888 ^7. Shell-growth in Cephalopoda ( Siphonopoda) . Ann. Mag. nat. 



Hist. 1: 298-310. 



— 1888 b. Prof essor Blake and shell-growth in Cephalopoda. Ann. Mag. nat. Hist. 1 : 



421-427. 



