792 SUMMAKY OF CUEEENT KESEAECHES EELATING TO 



for a long time, and Peden showed some resistance. Scyllarus could 

 bear 25°, but died slowly at 26°, and more quickly at 27° ; Palsemon 

 died at 26°, Hippocamjpns bore 27° well, and lived for an hour at 30°. 

 Other series of observations were made on the eflfects of increasing 

 the temperature to which the animal was subjected. 



Many marine animals were found to bear high degrees of tem- 

 perature for an astonishingly long time, as Actinise, Murex, Tethys and 

 Ajplysia. But it is not yet certain what heat they can permanently 

 bear. It is also important to discover how winter animals comport 

 themselves towards increase of temperature, and especially animals 

 such as the Heteropoda and Phronima, which are quite wanting in 

 the summer ; from what we know we must suppose that at the 

 beginning of summer, when the temperature of the sea becomes 

 raised, they make their way to greater depths, where the heat is 

 less. 



MoUusca. 



Mid-gut Gland (Liver) of the MoUusca.* — Dr. J. Frenzel, who 

 has already studied the mid-gut gland or so-called " liver " of the 

 Crustacea, now gives an account of his observations on the similarly 

 named organ in the MoUusca. The description of the glandular 

 epithelium commences with an account of the granular cells, which 

 are only completely wanting in the Cephalopoda ; each cell contains 

 in addition to the protoplasm and the nucleus, a vesicle which 

 incloses a number of more or less strongly coloured grains, fatty 

 spheres of various sizes, and often numerous albuminous masses. 

 The number of the grains varies remarkably even in one and the 

 same species, and their size is, also, subject to considerable variation ; 

 they have a definite and characteristic coloration, but this varies in 

 species and even in individuals ; the colouring matter is not diffused, 

 but there are clearer and darker spots. These cells are never absent 

 from Lamellibranchs, where the small coloured granules are spherical 

 in form, have a smooth contour, and are generally brownish-green or 

 yellowish-brown ; in the Prosobranchiata they are often of a pale 

 yellowish-brown colour, are wrinkled, and contain a number of 

 albuminous masses ; in the Pulmonata they are bright yellowish- 

 brown ; in the Pteropoda they are markedly brown, and in the 

 Cephalopoda they are absent. 



After discussing their chemical properties the author passes to 

 the club-shaped ferment-cells, which differ indeed in form in 

 various molluscs, but are always referable to a common type ; they 

 are absent from the Chitons and Patella, and probably also from 

 Pteropods and Fissurella. It it doubtful whether they are to be seen 

 in certain Lamellibranchs. 



Like the granular cells they contain a vesicular secretory ball 

 which contains a more or less strongly coloured body of fluid, mucous, 

 or semi-solid consistency ; in addition to it there are fat-drops, 

 albuminous masses, and, in some cases, crystals. They vary in size 

 in different forms, and are club-shaped or pyriform ; the liver secre- 



* Arch. f. Mikr. Anat., xxv. (1885) pp. 48-84 (1 pi.). 



