222 



M. WEISS 



into the body. In both families it is transformée! into a part of the digestive gland 

 (liver) at the beginning of postembryonic life. 



In the second half of the embryonic period and at the beginning of post 

 embryonic life the résorption of albumen takes place mostly in the two sacs of 

 the latter digestive gland. Some of their cells develop a transitory structure, 

 resembling that of the cells of the albumen sac. The définitive structure of the 

 epithelium of the digestive gland is only fully attained after the first few post- 

 embryonic days. 



Shortly before hatching, the embryo absorbs the rest of the albumen that 

 is still contained in the egg. This albumen is stored in différent ways in the body 

 of the two families of slugs: in the Limacidae, this reserve lies mostly extracellul- 

 arly in the wide lumen of the digestive gland and in the much dilated stomach; 

 in the Arionidae, it is accumulated intracellularly in the albumen cells of the 

 digestive gland, which is divided into numerous lobes. 



Through the différent ways of storing albumen varieties can be traced in the 

 two families, which appear during transformation of the transitory to the défin- 

 itive structure of the digestive gland and in the development of the stomach. 



The occurrence of the larval organs (cephalic vesicle, podocyst, larval nephri- 

 dia, ciliated band in the oesophagus, larval heart (Limax)) and the formation 

 of transitory structures in the midgut show that there is a complicated meta- 

 morphosis even in the intracapsular, so called direct development of the Pul- 

 monata. 



LITERATURVERZEICHNIS 



Abolins-Krogis, A. 1965. Electron microscope observations on calcium cells in the 

 hepatopancreas of the snail Hélix pomatia L. Arkiv for Zoologi, 18, 

 85-97. 



Barfurth, D. 1883. Uber den Bau und die Funktion der Gastropodenleber. Arch. f. 



mikrosk. Anat., 22, 473-524. 

 v. Beneden, P. J. und A. Windischmann. 1841. Recherches sur l'embryogénie des 



Limaces. Mùller's Archiv f. Anat. u. Physiol., 176-195. 

 Biedermann, W. und P. Moritz. 1899. Uber die Funktion der sogenannten Leber der 



Mollusken. Pflugers Arch. f. d. ges. Physiol., 75, 1-86. 

 Billett, F. und S. McGee-Russel. 1955. The histochemical localisation of ^-Glucuroni- 



dase in the digestive gland of the roman snail Hélix pomatia. Quart. J. 



micr. Sri., 96, 35-48. 



Bloch, S. 1938. Beitrag zur Kenntnis der Ontogenèse von Siisswasserpulmonaten mit 

 besonderer Berûcksichtigung der Mitteldarmdriise. Rev. Suisse de Zool., 

 45, 157-220. 



Brock, J. 1886. Die Entwicklung des Geschlechtsapparates der stylommatophoren Pulmo- 

 naten, nebst Bemerkungen uber die Anatomie und Entwicklung einiger 

 anderer Organsysteme. Ztsch. f. wiss. Zool., 44, 333-395. 



