170 SUMMARY OF CURRENT RESEARCHES RELATING TO 



granular, cystic, and mucous. But besides this series ending in mucus- 

 formation, there is another series ending in ferment-formation. Muco- 

 cytes have to be distinguished from zymocytes. Some of the cells, 

 especially those of punctate and alveolar aspect, show remarkable 

 chromophilous formations. Three ergastoplasmic differentiations are 

 described. The authors also describe the various stages in the matura- 

 tion and dissolution of the grains of zymogen. 



Spinning Gastropods.* — L. Lindinger has an interesting note on 

 Gastropods which form firm threads of mucus. He has observed the 

 process in Agriolimax agrestis, A. Icevis, Limax arborum, L. variegatus, 

 and in various species of water-snail {Ancylus, Bythinia, Physa, 

 Planorbis). Some of the terrestrial forms often let themselves down 

 from a leaf by a thread ; some of the aquatic forms use the thread both 

 in ascent and descent. 



Embryology of Physa fontinalis L.f — A. Wierzejski gives an ex- 

 haustive account of the segmentation up to the 123-celled stage, includ- 

 ing a consideration of the development of certain larval and adult 

 organs. He summarises his results in thirty-five conclusions. He has 

 found no evidence of an early localisation (in Conklin's sense) of organ- 

 forming substances in single blastomeres. From cells of the same 

 origin diverse organs may arise, e.g. from the descendants of an early 

 blastomere (4rf) were traced the larval kidneys, muscles, and connective 

 tissue, with probably also the heart and sex-glands. There is, in fact, 

 no reliable evidence for a rigid homologising of the blastomeres and 

 germinal layers. 



Heart and Arteries in Diotocardia.:}: — J. Spillman has investigated 

 the structure of the central vascular system in the Diotocardia, including 

 the histology of the heart muscle, the arteries, and the lacuna. The 

 Diotocardia show in the anatomical structure of their hearts significant 

 differences, such that, from this point of view, their separation into 

 Rhipidoglossaj and Docoglossas seems justified. The Rhipidoglossae have 

 a ventricle which is pierced by the hind gut. They possess two auricles 

 which in some cases close towards the ventricle by lamellar valves. The 

 ventricle in the Docoglossas is not pierced by the gut. There is only 

 one functional auricle — the left — which possesses a tube-like valve. 

 Whilst the ventricle in Rhipidoglossse passes directly into the aorta, in 

 the Docoglossae there is a bulbus arteriosus, which always lies outside the 

 pericardium. In the Ehipidoglossae there are pericardial glands with 

 secretory function, in whose cells are small rod-shaped crystals ; similar 

 crystals occur in the epithelial cells of the left kidney. 



Prototracheata. 



Monograph of Onychophora.§ — E. L. Bouvier has published the 

 first part of a monograph on Onychophora, which he dedicates to Prof. 



• Zool. Anzeig.. xxix. (1905) pp. 605-10. 



t Zeitschr. wiss. Zool., lxxxiii. (1905) pp. 502-706 (10 pis. and 9 figs.). 



X Jena Zeitschr., xxxiii. (1905) pp. 537-88 (3 pis. and 2 figs.). 



§ Ann. Sci. Nat. Zool., ii. (1905) pp. 1-240 (96 figs.). 



