ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
197 
of the cells is accompanied by the formation of vacuoles. Some of these 
at least are intercellular in Triclads, but they are always intracellular 
in Poly clads. The division of the parenchymal tissue into connective 
bars and connective cells must be given up. 
These Turbellaria always have a large number of glands in their 
body, and most of them are dermal. Some open into the pharynx and 
these may be regarded as salivary glands. The pharynx itself is very 
elaborately constructed. The form of the enteron is greatly influenced 
by the degree of development of the generative organs, and there is no 
doubt that in young animals, where these parts only exist in rudiment, 
the form of the enteron is much more regular and straight. Respi- 
ration appears to be effected through the walls of the enteron and of the 
body as well as by means of the water- vascular system. 
With regaid to the structure of the nervous system the author agrees 
with Leydig and Nansen in regarding the substance which fills Haller’s 
plexus as the hyaloplasm of Leydig and as the true nervous substance, 
but he differs from Nansen in so far that he believes that the fibres and 
fibrils of this nervous substance form a network and anastomose with one 
another. 
In the eyes of all alloiocoelous Turbellaria we may distinguish a 
pigment layer or pigment cup, refractive media or lens-cells, and per- 
ceptive media or a retina. In the last the layer of rods must be dis- 
tinguished from the optic nerve. There is much in common between 
the eyes of Alloiocoela, Triclads, and Polyclads, but the two last most 
resemble one another in the structure of the retina. The complete 
absence of lens-cells in Polyclads and Planarians is to be noted. 
In treating of tactile organs Dr. Bohmig points out that at the base 
of the tentacle there are numerous ganglionic cells, the processes of which 
form a small accumulation of dotted substance, whence fibres pass into 
the tentacles. He does not know whether the central part of these 
tentacles is filled by nerve-fibres or whether parenchymatous tissue 
is also there present. In the epithelium of a comparatively well- 
extended tentacle peculiar bodies were found just beneath the cuticle ; 
these possibly represent nerve-end-organs, but no connections with 
nerve-fibres were detected. These bodies are exceedingly small and 
have the form of lenses ; in the middle of the more convex surface there 
is a small round spherule from the surface of which fine stride radiate ; 
these striae appear to be continued into minute and fine hairs. 
Some considerable space is devoted to the generative organs. 
In the second portion of his paper Dr. Bohmig deals with the 
anatomical characters of Plagiostoma Girardi , both large and small 
varieties, the latter of which is new, P. reticulatum, P. siphonophorum , 
P. maculatum , P. bimaculatum , P. dioicum, P. lemani ; Vorticeros auri- 
culatum is next considered. Among the Cylindrostomina we find a 
new genus Monoophorum for M. striatum sp. n. ; the genus is defined 
as belonging to the Cylindrostomina and as having a common oral and 
genital orifice which is situated near the hinder end of the body ; 
the pharynx is directed backwards and the penis forwards ; the bursa 
seminalis communicates with the genital atrium ; the rudiments of the 
two yolk-glands are fused in the median plane on the dorsal side. In it as 
in Cylindrostoma the testes are situated more anteriorly than in Plagio- 
