| OCR Text |
Show 1^03.] FROM EAST AFRICA AND ZANZIBAR. 385 most are set almost at right angles to the rhachis. The stomach is large and free, but thin and not laminated nor muscular. The blood-gland is large, and the nervous system is very concentrated. The generative system appears to be as described by Bergh, but the glandula and hasta amatoria are difficult to see and were satisfactorily detected only in one specimen. These specimens are, I think, clearly Ehrenberg's Asteronotus hemprichi, from Massaua. He describes it as " sex-pollicaris, oblongus, glaber, vesiculosus, supra fuscus, lineis circulisque niveis sparsis, vesicas dorsuales cingentibus, subtus lateritus, pecle flavido, branchiarum apertura lobulis sex stellatim positis praecludenda. . . . . Branchiarum e dilute laterito seu carneo albicantium fasciculus amplus." Prof. Bergh seems inclined to think (S. R. xvii. p. 917) that the real species of this genus are not more than three, hemprichi, mabilla, and ccespitosus. The differences between these three do not seem to me to be clearly defined, and m y numerous specimens, which I unhesitatingly refer to one species, present connecting links, especially in colour, which make me think that the three species are merely varieties of one. EXPLANATION OP THE PLATES. N.B.-Except in the cases noted, the figures are drawn from the living animal. PLATE XXXII. Fig. 1. Thordisa villosa (p. 367), ventral view. 2. Dorsal view of the same. 3. Thordisa crosslandi (p. 368), ventral view. The manrin of the mantle i* in turned here and there, showing the mohile papillae which cover the dorsal surface. 4. Trippa monsoni (p. 371), dorsal view, much enlarged. 5. Halgerda willeyi (p. 372), from a drawing by Dr. Arthur Willey. PlATE XXXIII. Fig. 1. Thordisa villosa (p. 367), head and anterior end. The figure shows an extreme elevation of the body, which normally is flat. 2. Dorsal papilla of the same species, with flexible pigmented end and spicule-stiffened base. Also a portion of the mantle-edge magnified. 3. Branchiae of the same. 4. Thordisa crosslandi (p. 368). Teeth from the radula: a, upstanding; b, laid flat. 5. Gills and anus of the same. A ridge (a) connects the higher part of the rhachis with the anal papilla (b). 6. Dissection of the retracted penis of the same, showing the shape and structure of the enclosed glans. 7. The glans penis of the same is slit open, showing it to be hollow and to contain a prolongation of the vas deferens which passes to its tip. 8. The central nervous system of the same in its sheathing of connective tissue. PLATE XXXIV. Fig. 1. Halgerda wasinensis* (p. 373), dorsal view. 2. Diagram of the arrangement of its gill on the rhachis. 3. Sclerodoris coriacea (p. 383). Pencil drawing from the preserved specimen. 4. Degenerate Copepod parasite found in the liver of Sclerodoris (p. 384). 5. Asteronotus hemprichi (p. 384). 6. Enlarged view of the gill-opening when the branchiae are as completely retracted as is possible. 7. Kentrodoris rubescens (p. 374), about half natural size. * This name is wrongly spelt " wassinensis" on Plate. PROP. ZOOL. Soc-1903, YOL. II. No. X X Y . 25 |
