178 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
and the suggestion of Barrois that it serves, along with the gelatinous 
layer in the stomach, to protect the walls of the gut by surrounding 
sharp particles with mucus, is accepted by Schulze as most probable. 
He compares its functions to that of the epithelial glands which lie near 
the internal apertures of the gill-clefts in Batrachian larvm. 
Renal Function of Acephalous Mollusca.* — M. A. Letellier has 
investigated the renal function in Pecten and Ccirdium. He finds that 
the organ of Bojanus gets rid of excess of water, urea, and various neutral 
nitrogenous bodies and phosphates, as well as, accidentally, uric acid. 
The organ of Eeber (gland of Grobben) extracts irom the blood the 
acid it contains ; in both the forms studied the acid was hippuric acid. 
Hermaphrodite Lamellibranchs.t — Prof. P. Pelseneer has con- 
tinued | his studies on the hermaphroditism of certain Lamellibranchs, 
and now asserts the existence of an entire group exhibiting herma- 
phroditism. Since describing Lyonsiella and Poromya he has made inves- 
tigations as to Tliracia , Lyonsia, ClavageUa , Myochama , and Cuspidaria ; 
and he now states that no form of the Anatinacea or Septibranchiata 
yet studied has been shown to have the sexes separate. We may con- 
clude that they are hermaphrodite, but the male and female gonads 
separate — an arrangement not known in any other Mollusc. This dis- 
position of parts does not certainly indicate a condition once common 
to the whole class, as Gegenbaur believes, for all the hermaphrodite 
Lamellibranchiata are specialized, while the most archaic forms (the 
Protobranchiata) are not only dioecious, but have never presented an 
example of such partial hermaphroditism as may be sometimes seen in 
the Frog or the Herring. 
Otocysts of Nuculid8e.§ — Prof. P. Pelseneer shows that the Lamelli- 
branchiate Nuculidae have, at all ages, otocysts which communicate freely 
with the exterior, and they are the only known Mollusca in which this 
arrangement is found. The possession of this archaic character con- 
firms the opinion several times expressed by the author that the Nucu- 
lidae are the most primitive of existing Lamellibranchs. In addition 
to the evidence afforded by the gills, the nervous system and the renal 
and generative organs, there are other points which Dr. Pelseneer pro- 
mises to communicate later on. 
Molluscoida. 
a. Tunicata. 
Embryonic Development of Pyrosoma.|| — Prof. W. Salensky states 
that the egg of Pyrosoma is meroblastic. Before fertilization a certain 
number of cells make their way out from the follicular epithelium ; 
these may be known as calymmocytes. During segmentation the calym- 
mocytes make their way in between the blastomeres and take part in 
the formation of the body of the embryo ; they undergo a considerable 
change in their protoplasm and nuclei. The differentiation of the ger- 
minal layer commences with the division of the segmented germ into an 
* Comptes Rendus, cxii. (1891) pp. 56-8. 
f Zool. Anzeig., xiv. (1891) pp. 5-8. $ See this Journal, 1890, p. 448. 
4 Zool. Jalirb. (Abtli. f. Anat. u. Ontog.), iv. (1890) pp. 501-4. 
\\ T. c., pp. 425-77 (3 pis.). 
