ZOOLOGY AND BOTANY^ MICKOSCOPYj ETC. 209 



speak of wide-branched cavities in the tissues, the walls of which are 

 merely formed by connective substance, and which have been indi- 

 vidualized and made independent of the tissues of the organs, then 

 there are not here lacunae. 



In addition to the contractions of the heart, the author has observed 

 rhythmical contractions in the pulmonary vein and its branches. The 

 ventricle is expressly stated to bo innervated from a nerve-plexus, 

 which supplies also the aorta, while the auricle appears to be inner- 

 vated by a pulmonary nerve ; after great trouble Nalepa was able to 

 demonstrate nerves in the musculature of the auricle. 



After some account of the lung, attention is directed to the kidney, 

 and it is shown that Meckel was in error in supposing that there was 

 a true cameration of the organ, and that the chambers communicated 

 by lateral orifices with the ureter ; it seems rather that folds project 

 from its upper and lower walls, but that there is a common central 

 cavity, which, at the tip of the kidney, communicates with the ureter. 

 The lamellse are ordinarily largely connected by transverse folds, and 

 the spaces thus formed are lined by a secretory epithelium ; the uric 

 acid excreted appears to be partly free and partly united with other 

 bodies to form guanin. 



The penis of Zonites and Limax is distinguished from that of 

 Helix by the absence of a flagellum ; and there are certain differences 

 in the vascular supply. The papillae of stimulation found in the 

 penis of Zoonites consist largely of cells of connective substance, 

 imbedded in intercellular substance, and bounded by the epithelium 

 of the inner surface of the penis. The organ is richly supplied with 

 nerves, as may be well seen in chloride of gold preparations of Limax ; 

 the ganglionic cells are arranged in groups, are rounded, and have 

 very large nuclei. A glandular mass in the wall of the vagina of 

 Zonites corresponds to the digitated mucous glands of the Helicidae ; 

 it consists of tubular follicles which open separately into the vagina, 

 and are lined by a high glandular epithelium. With these the 

 follicles of the bursa copulatoria agree in structure and form. 



Segmental Organs and Podocyst of Embryonic Limacinae.* — 



S. Jourdain finds that at the time of the formation of the stomodaeal 

 invagination, there appears on either side a lahio-tentacular thickening, 

 placed in front of the pallial plate. There is a prepallial swelling 

 formed of a central nucleus of granular matter, which the author regards 

 as true post-embryonic yolk-material, destined to make up for the in- 

 sufficient quantity of primitive yolk. The segmental organ is paired, 

 and is siphonate in shape, the convexity being superior or dorsal ; it 

 consists of a membrane lined by polygonal cells with a large granular 

 nucleus, and with very fine cilia ; the external orifice is funnel-shaped. 

 It has no relation to the permanent kidney, which is developed inde- 

 pendently. The fate of the segmental organ, no vestiges of which 

 are to be found in the adult, has not been determined. The term 

 " podocyst " is applied to the contractile appendage of the hinder part 

 of the mouth, which is either short, as in Limax agrestis, or elongated 



* Oomptes Eendus, xcviii. (1884) pp. 308-10. 



