ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 65 



cells are the products of their division. The female germ-gland 

 forms a band-shaped organ, which lies beneath the intestine, and 

 consists at its hindermost end of indifferent, and at its anterior end of 

 ovarian, cells. The female orifice lies in the ventral median line, and 

 there is a feebly developed vagina, with which are connected some 

 glandular cells. The female organs are, on the whole, as much of the 

 type of those of other Rhabdoccela as are the male. 



The excretory system opens, at the level of the female pore, on 

 either side of the body; connected with this is a short terminal canal 

 with firm contractile walls. For other points reference is made to 

 the accounts o*' earlier observers. 



The paper concludes with the description of P. halticua n. sp. 



Monograph on the Turbellarians.* — Prof. L. von Graff has pub- 

 lished a splendid monograph of this group, founded on elaborate 

 personal investigations. 



Separating the Nemertines altogether from the Turbellarians, he 

 divides the group into I. Ehabdocoelida, and II. Dendrocoelida. In 

 the definition given of the two sub-orders, an interesting point of 

 difference is brought out, namely, that in the former the yolk-glands 

 are always present in the form of a pair of compact glands, whereas 

 in the latter they are always divided up into numerous separate 

 follicles. 



The Ehabdocoelida are divided into three groups : — (1) Acoela ; 

 (2) Ehabdocoela; (3) Alloiocoela, which are thus defined: — 



(1) Acoela. With digestive internal substance ; without differen- 

 tiation of a digestive tract and parenchym tissue. Without nervous 

 system or excretory organs. All forms as yet known provided with 

 an otolith. 



(2) Ehabdocoela. — Digestive tract and parenchym tissue differ- 

 entiated ; a roomy body-cavity usually present, in which the regularly 

 shaped intestine is siispended by a small amount of parenchym tissue. 

 With nervous system and excretory organ. Generative organs 

 hermaphrodite (except in Microstoma and Stenostoma). Testes, as a 

 rule, two compact glands. The female glands present as ovaries only, 

 ovario-vitelligenous glands, or separate ovaries and yolk-glands. 

 Genital glands separated from the body parenchym by a special 

 tunica propria. Pharynx always present and very variously con- 

 structed. Otolith absent in most cases. 



(3) Alloiocoela. — Digestive tract and parenchym tissue differ- 

 entiated, but the body-cavity much reduced by the abundant de- 

 velopment of the latter. With nerve system and excretory organ. 

 Generative organs hermaphrodite, with follicular tests and paired 

 female glands, either ovaries only, or ovario-vitelligenous glands, or 

 separate ovaries and yolk-glands. Yolk-glands irregularly lobular, 

 rarely partially branched. Genital glands almost always without any 

 tunica propria lodged in the spaces in the body parenchym. Penis 

 very uniform, and either without chitinous copulatory organs, or with 



* Graff, L. von, ' Monographie der Turbellarien. 1. EhabdoccBlida.' Fol. 

 Leipzig, 1882, 12 figs, and 20 pis. Cf. Prof. H. N. Moseley in ' Nature,' xxvii. 

 (1883) pp. 227-8. 



Ser. 2.— Vol. III. F 



