ZOOLOGY AND BOTANY, MICROSCOPY, ETC, 957 



central nucleus of the brain into a homogeneous mass. In tho ventral cord 

 we find, below the central mass of nerve-fibres, a hyaline structureless space, 

 which corresponds to what other authors have called a giant nerve-fibre. 

 M. Jourdan refuses to regard this structure as nervous, and looks upon it 

 as being an organ of support for the ventral nervous system. Among the 

 investments of the cord is a pigmented mass, which is specially accumulated 

 above it. This mass is lodged in a plexus of cells with branched and 

 anastomosing prolongations, and the cells themselves appear- to be com- 

 parable to the i^lasmatic cells of the connective tissue of vertebrates. 



After some account of the process of regeneration of the central nervous 

 system, the author passes to the sensory organs, where the antenufe are first 

 described ; the eye has a crystalline lens provided with a capsule, formed 

 by the folding over of a delicate portion of the body- wall ; the body of the 

 lens itself is semi-liquid, and is, possibly, analogous to the mucus secreted 

 by the animal ; the cells beyond it form the retina and vitreous body, and 

 are nothing more than modified epithelial cells of the hypodermis ; the 

 author compares this simple eye with those of Patella, of Lamellibranchs, 

 and with the simple eyes of Insects. 



The digestive tract exhibits no indications of any glandular organ ; the 

 gills are essentially formed of two vessels covered by a layer of longitudinal 

 muscles, and protected by an epithelium which is similar to that of the 

 general surface of the body. The author thinks that there is no endothelial 

 lining to the vessels of the Chtetopoda ; but as this would be a remarkable 

 divergence from \vhat obtains in other forms, he thinks it ought to be 

 verified. 



The observations on the " pedal glands," the lateral pigment-organs, 

 and the segmental organs are collected into one chapter, as these parts have 

 been long regarded as the same. The term of pedal gland is applied to 

 the organ which Claparede regarded as pouring its secretion on to the 

 setae. Immediately beneath the setje of each segment there is a mass of 

 cells, which form a sort of epithelial bud on the internal surface of the 

 integument. A superficial examination will suffice to show that these cells 

 do not differ from the glandular elements which are found in the epidermis. 

 They are so pressed against one another as to form a sort of multilobate 

 racemose gland, the j^roduct of which passes to the exterior by a number of 

 pores; these glands are better developed in Eunice Harassii than in E. 

 torquata. The lateral j)igment-organs were rightly regarded by Claparede, 

 in opposition to Ehlers, as quite independent of the segmental organs ; as 

 to these last, which are very difficult to observe in most species of the 

 genus, the great Swiss naturalist was unable to detect the external orifice. 

 M. Jourdan comes to the conclusion that the organ opens to the exterior 

 immediately below the pedal gland ; the peripheral portion is formed of a 

 membranous tube with flat cells on either surface, and appears to be rather 

 an efterent vessel for the genital products than an organ of secretion. 



Nervous System of Opheliaceae.* — Dr. W. Klikenthal gives a detailed 

 account of the structure of the nervous system in the Opheliaceae. 



Along the median line of the ventral surface there extend two parallel 

 strands, which diverge and run to points at both ends, forking anteriorly so 

 as to surround the gut. In two regions the strands are united, in the 

 anterior portion of the head, and along the whole region from the anus to 

 the third tail-segment. The two fibrous strands are surrounded by groups 

 of ganglion-cells, and a common neurilemma ensheathes the entire system. 

 Each segment contains two or three ganglionic aggregations. These give 



* Jenaiscl). Zeitschr. f. Xaturwiss., sx. (1SS7) pi\ 511-80 (3 pis.). 

 1887. 3 B 



