370 Miscellaneous. 



united by broad and short coniraissures. The supra-cesophageal 

 ganglion extends nearly to the divisional furrow, the lower one to 

 close by the genital aperture. iVom the former originate the nerves 

 for the forcipate chelas and the palpi : the latter emits nerves for 

 the buccal organs, and further on each side four nerve-trunks for 

 the limbs, and posteriorly nerves into the abdomen. In structure 

 the central nervous system of the TyrogJijphi agrees with that of 

 the Arthropoda. The ganglion-cells are unusually small. The 

 central substance presents a finely fibrous structure only under a 

 very high power. It is an interesting fact that in the infra-ceso- 

 phageal ganglion the ganglion-cell layer occurs only on the under- 

 side. The nerves are very transparent and abound in rounded 

 nuclei. 



Th.e female sexual organs consist of two germ-glands situated on 

 the two sides of the anal fissure. The two oviducts run at first side 

 by side along the ventral surface nearly to the external genital 

 aperture, then turn backwards, and afterwards make another curva- 

 ture forwards. Before reaching the genital aperture, the two 

 oviducts unite to form a vagina. The space above the two ovaries 

 is occupied by a vesicle, first described by Eobin, and interpreted 

 by G. Haller as a seminal vesicle. This notion would be supported 

 by the innumerable quantity of cells which I found in this vesicle 

 imbedded in an albuminoid mass, and which, from their size and 

 form, 1 must regard as seminal corpuscles. I have been hitherto 

 unable to demonstrate with certainty any union between this vesicle 

 and the oviducts, which would place its interpretation as a seminal 

 vesicle beyond doubt. The wall of the female sexual apparatus con- 

 sists of a delicate tunica propria and a variously formed epithelial 

 layer. In the first part of the oviduct the cells are low and small ; 

 in the dilated terminal portion, on the contrarj', large, nearly 

 cubical, and without distinct limitation. The ova are by no means 

 developed in follicles, which become constricted off and pass into 

 the body-cavity, but they become differentiated on the periphery of 

 a central nucleated protoplasmic mass (germ-magazine) by a portion 

 of the common plasma loecoming cut off into a distinct cell-body 

 (ovicell) around an enclosed nucleus. The ovicells are surrounded 

 by a distinct vitelline membrane. The germinal vesicle is round and 

 clear ; the vitellus at first finely granular. Subsequently strongly 

 refractive vitelline vesicles make their appearance, which soon com- 

 pletely conceal the germinal vesicle. After the ovum has attained 

 its definitive size and form, it becomes surrounded by a shell, which 

 is furnished by the epithelial cells of the oviduct. The external 

 genital organs are rather complex in structure. In the male, as in 

 the female, they are covered by two membranous sacs, each of 

 which conceals two suckers. These are hollow cones, of which 

 the side walls are strongly chitinized. The sucking disk, on the 

 contrary, is a soft thin membrane. To it is attached a muscular 

 bundle which lies in the axis of the sucker, and serves to pull back 



