ZOOLOGY AND BOTANY, MICROSCOPY, ETC. C43 



There is notbing peculiar in the general anatomy of this Gephyrean, 

 as seen by the naked eye. The author gives the name of skeletal tissue 

 to a peculiar form found in tlie collar and tentacular crown. The cells 

 composing this tissue are roundish, witli large nuclei, and their proto- 

 plasm is traversed by numerous fine lines. It seems to support and 

 strengthen the structures in which it is found, and from its jjosition 

 serves as a firm hold for the insertion of the retractor muscles of the 

 introvert which are attached just behind it. The cavity of the ali- 

 mentary canal is diminished by numerous ridges. There are two kinds 

 of blood-corpuscles, the larger of which are found in the body and are 

 oval in outline, with a spherical nucleus. The smaller are found in a 

 closed series of spaces, usually termed the vascular system, Tliis space 

 may be described as consisting of three parts all communicating with 

 one another, and the whole is lined by a flat epithelium. 



Each nephridium consists of a bladder and a true secreting part ; 

 both are well supplied with muscular fibres, and are very contractile. 

 The bladder ojiens to the exterior by a circular mouth and to the 

 interior, or body-cavity, by a ciliated opening which has the shape of a 

 flattened funnel. The lumen of the secretory part is broken up into a 

 number of side chambers, and the whole is lined by a very peculiar 

 epithelium ; the cells of tliis are columnar in shape, and are crowded 

 with minute spherical granules ; many of them have at their free end a 

 bubble or vesicle in which these granules accumulate. From time to time 

 these vesicles break off, and lie in the lumen of the secretory part of 

 the bladder ; they are no doubt extruded from the body. The whole 

 process is very like the secretion of milk in a mammary gland. In both 

 sexes the rej)roductive organs form fimbriated ridges, which are attached 

 to the bases of the ventral retractor muscles, and are continuous across 

 the interspace between the two, ventral to the nerve-cord. The cells 

 forming these ridges are continuous with the peritoneal lining of the 

 body- wall. 



The ganglion cells of the brain are mostly small and bipolar, but 

 on the posterior surface there are a certain number of unipolar giant 

 ganglion cells, at least four times as large in diameter as the smaller 

 cells. The ventral nerve-cord has no trace of a double origin or of 

 segmentally arranged ganglia. The sensory organs are represented by 

 sensory pits in the brain, and by ectodermal sense-organs in the 

 introvert. 



•y. Platyhelmiuthes. 



Otoplana intermedia.* — Dr. G. du Plessis gives a short account of 

 this interesting new Turbellarian found near Nice ; it is one of the 

 few known marine Triclads. It is blind, and has no trace of external or 

 internal eyes, or even of eye-like pigment-spots. There is, however, a 

 frontal otocyst of just the same structure as that of all the Monotidae. 

 Eight and left of it there are two dorsal ciliated fossets similar to those 

 of Nemertines and of the Cylindi'ostomata, which are very near Monotus. 

 The periphery of the body is provided at equal intervals and on either 

 side by tactile setse arranged symmetrically in pairs. On the frontal 

 edge they are very robust at the base, and have the form of strong 

 spines. The brain, which is discoidal, aud the nerves which are given off 

 from it are similar to those of the Monotida^. The skin also resembles 



* Zoo]. Anzeig., sii. (ISSii) pp. 330-42. 



