INVERTEBKATA, CRYPTOGAMIA, MICROSCOPY, ETC. 2G5 



into any description of them were it not that the results attained to 

 are so divergent. He finds then that in both Bhynchodesmus and 

 Geodesmus there is on the ventral side of the body and behind its 

 central region a fine orifice, which can scarcely be seen in the living 

 animal, but which leads into a wide space leading into a long bell- 

 shaped pharynx ; this pharynx is only protrusible in the same sense 

 as is the human tongue, but the animal must push out its pharynx to 

 be able to eat ; whether the pore referred to should be correctly 

 denominated the mouth, embryological investigations can alone deter- 

 mine. A transverse section through this pharynx reveals the presence 

 of a fine homogeneous layer provided with numerous but short cilia ; 

 below this, there is a thin but compact layer of longitudinal muscles, 

 and then there comes a circular layer ; in the subjacent connective 

 tissue unicellular glands, and indications of nerves are to be dis- 

 covered. Nor is this all ; next there is a layer of longitudinal 

 muscular fibres, which are more distinctly separated into bundles, 

 then there is more connective tissue, and then a thick layer of circular 

 muscles, whence muscle fibres radiate out to the periphery; the 

 arrangement is much the same, though not altogether similar, in the 

 fresh-water Planarians. The enteric tract is throughout provided 

 with a simple and high cylindrical epithelium, the cells of which are 

 closely appressed and are set obliquely to the axis of the enteron ; 

 these cells are directly connected with the surrounding connective tissue. 



As to the structure of the generative organs proper the author 

 finds himself in complete agreement with Mr. Moseley ; the gene- 

 rative products seem, in these hermaphrodites, to be developed at 

 different times, and this is the cause of Kennel's earlier statement 

 that Geodesmus had only one pair of testes ; he now corrects this in 

 saying that there are in it six pairs. The character of the yolk- 

 glands and their different ducts required careful investigation : the 

 results of Dr. Kennel show that in the fresh-water Planaria, with one 

 pair of ovaries, there are to be found, in all the sections almost from 

 the anterior end of the body as far as the generative organs, packets 

 of large cells which may be finely or coarsely granular ; these cells 

 make up the yolk-glands ; the ducts are numerous and short, and 

 open at the point where the oviduct joins the vagina. In llhyncho- 

 desmiis, Geodesmus, and Planaria luguhris the yolk-glands only open 

 into the outer side of the oviducts, but in Dendroca;lum the arrange- 

 ment is much more complicated ; where the duct of the yolk-gland 

 opens, the oviduct is connected with a large vesicle. The author tlien 

 gives a careful accoimt of tlie arrangement of the various parts of tho 

 generative organs, which is beyond an abstract. 



Passing X)n to the nervous siistem, the cerebral ganglion of tho 

 land Planaria is described as lying in the most anterior region of tho 

 body, and as forming a rounded mass consisting of two syunnetrical 

 halves ; tho mass of the brain is made up of a very finely granular 

 dotted substance and of small cells, which are most numerous where 

 the two halves ap^jroxiiiiate. Although they have not the character of 

 " typical" ganglionic cells, tlu^y must be regarded as ncjrve-cells, and 

 as completely similar to the smaller colls which are found interspersed 



