INVEETEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 443 



characters, which leads the author to regard it as intermediate 

 between the AcoeLate and the Coelate type. In most cases, a trans- 

 verse section reveals no enteric Inraen, and, even where one does 

 seem to be present, it is easy to see that it is due to an artificial 

 rupture of the tissue. Longitudinal sections reveal the fact that the 

 ventral and dorsal walls differ in character ; the former has a low 

 epithelium, the cells of which are with difficulty distinguished. 

 There is a small round nucleus and larger and smaller vacuoles can 

 be made out in the protoplasm of the cells. The cells of the upper 

 wall are much longer, and are not all placed in the same plane ; 

 their vacuoles are of considerable size ; it is only in the most 

 anterior portion that it is possible to see any indications of a 

 lumen. 



The study of the generative organs is complicated by the necessity 

 of examining specimens of different ages, owing to the fact that, 

 in these hermaphrodites, the male and female elements are not 

 developed contemporaneously. In specimens 1 mm. long the two 

 testes with the large seminal vesicle and the penis are alone present ; 

 in completely gi'own forms the vesicle is diminished in size and the 

 testes have completely disapjiearcd ; but the female organs, consisting 

 of two long, band-shaped ovaries, two greatly ramified yolk-glands, 

 uterus, and receptaculum seminis, together with a number of uni- 

 cellular glands which open into the uterus and form the shell of the 

 egg-capsule, are exceedingly well-developed. There is a common 

 genital pore. It is only possible to note one or two points in these 

 organs : — 



(1) The accessory glands, said by Hallez to be so common in the 

 male Ehabdocojla, are altogether absent. 



(2) There are a number of nuclei in each testicular cell. 



(3) The spermatozoa seem to be provided with a delicate forked 

 process at one extremity ; but these are very difficult to detect. 



(4) The ovaries are remarkable for being long and band-shaped ; 

 and the yolk-sacs for their ramifications. 



The author concludes by pointing out some general results ; the 

 fact that Graffilla is the only lihabdocoele in which the pharynx is not 

 provided with a special sac or pouch, makes it necessary to form the 

 family GraJJillida for its reception. Wlien we come to ask what 

 relation this holds to the rest, we are brought face to face with the 

 division of the group into AcoeJa and Coelaia, on which Uljanin was 

 the first to insist. Later investigations seem to show that tlie presence 

 or absence of a ccclom is not a point of primary importance. The Acoela 

 share with the Ctclatc genera Macrostomum and Vera, the absence of 

 a pharynx and the union of the yolk-glands and ovaries — -these are the 

 Microstomida ; but as the absence of a pharynx is of importance, 

 we may place them in the division Apharyngea. The rest of the 

 Rhabdocoila form the Pharyngea and among them tlie Graflillida 

 occupy the lowest place. Tlio absence of a gastric cavity is of 

 importance as bearing on tlio Gastraja lluiory and on the i>rol)ability 

 of the descent of a Jiliabdocado from a I'lanrca or from an agastric 

 Infusorian ; Dr. von Ihcring inclines to the latter view. 



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