180 SUMMARY OF CURRENT RESEARCHES RELATING TO 



part is open to the exterior behind. In front it bends round, and 

 runs backwards to about the level of the 5th shell plate, where 

 it changes its character, and is continuous with (2) a duct containing 

 brown colouring matter in the columnar cells lining it, and receiving 

 no glandular C86ca. This part extends back to the level of the last 

 gill, where it turns outwards, and becomes continuous with (3) a part 

 running forward for a short distance close to the lateral nerve, and lined 

 by large ciliated columnar cells. This opens in front at the level of 

 the penultimate gill into the pericardium. The author expected to find 

 the communication between the two parts of the renal duct behind, 

 in the region of the bladder, and for some time was puzzled at not 

 finding it. Mr. Balfour however suggested that the communication 

 might possibly be found in front, reasoning from the analogy of the 

 structure of the kidney in other Mollusca, and on examining the 

 anterior part more carefully, the two parts of the gland were found 

 to be communicating. 



Morphology of Neomenia-* — Messrs. A. Kowalevsky and A. F. 

 Marion believe they have made the somewhat remarkable discovery 

 that all naturalists who have examined this form have mistaken the 

 posterior for the anterior end. They are enabled to show that the 

 " lateral glands " of Tullberg are salivary glands, and that the organ 

 called the radula is really the penis. The description of the present 

 writers is in accordance with that of Proneomenia as lately given by 

 A. A. W. Hubrecht ; "j" but we reserve details till the publication of 

 their fuller paper. 



In another paper | Hubrecht affirms his belief that it is the 

 authors and not previous investigators who have misunderstood the 

 matter. 



MoUuscoida. 



Organization and Development of the Ascidians.§ — A proper 

 body-cavity in the Ascidians has been found by E. van Beneden to 

 exist only in the larvte. The species chiefly examined were Phallusia 

 mentula, P. mamillata, Ciona intestinalis, Perophora listen and Clavel~ 

 Una Rissoana. 



The larval mesoderm is found to consist of a right and a left 

 lamina, derived from the primitive endoderm, and limited to the pos- 

 terior part of the body. Each of these plates is divided into a posterior 

 portion, formed of a single layer of cells, and giving rise to the 

 muscle-cells of the tail, and an anterior one, which in Perophora 

 and Clavellina is bilaminar and encloses a cleft opening into the 

 alimentary canal and roofed in above by the chorda dorsalis. 



At a later period the anterior mesodermic cells lose their epithelial 

 character, acquiring that of the adult blood-corpuscle, and becoming 

 distributed to the epiblast, the central nervous system, and the hypoblast 

 of the alimentary tract. A similar change comes over the endodermic 

 cells of the floor of the neuro-intestinal canal, and the scattered cells 

 give rise to the blood-corpuscles, the connective tissue, the body- 



* Zool. Anzeig., iv. (1882) pp. 61-4. f This Journal, ante, p. 31. 



X Ibid., pp. 84-6. § Comptes Renrlus, xcii. (1881) pp. 1238-41. 



I 



