ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 795 



are limited by Langer's vesicles are indeed witbout endothelium, but 

 not \vithout walls, which are generally formed by the membranes of 

 the mucous cells ; it is possible that here and there there is a very 

 slight fringe of protoplasmic substance bounding the lumen of the 

 vessels. 



Organs of Bojanus in Anodonta.* — Messrs. A. B. Griffiths and 

 H. Fellows have undertaken a series of experiments which they 

 consider to establish the renal functions of the organs of Bojanus of 

 the fresh-water mussel. 



Mimicry among Marine Mollusca.f — Mr. H. L. Osborn directs 

 attention to an observation by Mr. E. B. \\'ilson on Ovulum uniplicaium 

 — a mollusc which lives abundantly on the stems of the Leptogorgia 

 virgulata ; this sea-fan has a stem of an orange yellow colour, and is 

 often marked with yellow swellings where it has spread itself over 

 the shell of an attached barnacle. The Ovulum has a yellow shell, 

 and the skin is of an orange yellow colour. The author has dis- 

 covered a Leptogorgia of a deep rose colour mottled with white, and 

 living with it was an Ovulum of a similar coloration. If the red 

 snail and the yellow coral were put into an aquarium, the former did 

 not approach the latter. Another example is afforded by an un- 

 determined species of the nudibranch Scyllsea, which has the closest 

 resemblance to the Sargassum or gulf-weed ; this was not found on the 

 weed, and only one example of it was detected. Against this, how- 

 ever, we must put the fact that the creature is quite incapable of 

 swimming, and that it is not to be expected that it should be found 

 near land. 



Molluscoida. 

 a. Tunicata. 



Postembryonal Development of Phallusia scabroides (n. sp.).+ — 

 Prof. E. van Beneden and M. C. Julin in describing the postembryonal 

 development of a new species of Phallusia, state that their attention 

 was called to the persistence in the young Ascidian of the two dorso- 

 lateral orifices which put the peribranchial cavities into direct com- 

 munication with the exterior. They are of opinion that the proper 

 cloacal cavity ought to be sharply distinguished from the peri- 

 branchial cavities ; its floor is formed by the dorsal surface of the 

 body of the larva which undergoes a slow and progressive descent. 

 The cloaca, which is at first elongated transversely, becomes gradually 

 a cone of circular section, while the external branchial orifices 

 approach one another, and, finally, fuse to form the single and median 

 cloacal orifice of the adult. The cloacal cavity is bounded solely by 

 the epiblast, which, on the other hand, only bounds the outer part of 

 the peribranchial cavities, while their inner wall is perforated by 

 stigmata of hypoblastic origin. It is necessary to distinguish between 

 the primary stigmata, of which there are six, and the secondary that 

 arise by a kind of constriction, and of which there are six rows. The 



* Chem. News. li. C188i5) p. 241. 



t Science-, vi. (188.'5) i>\>. 0-10. 



X Arch, dc Biul., v. (1885) pp. Gil -38 (1 pi.)- 



