618 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
nature of this structure. The mesoderm takes no part in its formation. 
It may be compared with the so-called external primitive kidney cells of 
Prosobranch embryos, but the suggestion of a complete homology would 
be premature. 
Homalogyra.* * * § — M. A. Vayssiere has a preliminary notice of his 
investigation of this genus, formed in 1867 by the late Dr. Gwyn 
Jeffreys. He finds that it has two dorsal tentacles of some length, and 
that the radula has not been correctly delineated either by Sars or 
Jeffreys. He gives amended diagnoses of the family and generic 
characters. The species studied appears to be H. atomus , which was 
found for him off Marseilles. 
Structure and Habits of Jorunna Johnstoni.f — Mr. W. Garstang, 
in a short note on this Nudibranch, states that it lives on the same 
stones as the small Halichondrise which it so closely resembles. The 
form and general colour of the Mollusc and the Sponge are very 
similar, and there are even the same slight variations in tint. The only 
external difference is presented by the two dorsal tentacles of the Nudi- 
branch, but the presence of conspicuous spots on the back of the animal, 
coloured doubly like the tentacles, and arranged so that the tentacles 
are included in the same series, effectually deceives the eye and conceals 
almost entirely the projecting tentacles. It is to be remembered that 
the author has shown that sponges are shunned by predatory fishes 
under both natural and artificial conditions. 
Branchial Sensory Organs of Patellidge.j: — Dr. J. Thiele describes 
an organ in Patina pellucida which forms a knob-like projection of the 
epithelium, at the sides of the body between the foot and the mantle. It is 
supplied by a delicate nerve from Spengel’s olfactory ganglion, which is 
somewhat difficult to detect between the fibres of the retractor muscle. 
The epithelial band presents the characters of sensory epithelium. 
Neomeniid3e.§ — Dr. H. Simroth begins his study of these interesting 
types with a compact summary of what is known in regard to their 
structure. Passing over this we find the following genera suggested for 
the twenty-six known species : — Genus I. Neomenia Tullberg ; II. Pro- 
neomenia Hubrecht ; III. Solenojpus Sars ; IY. Phopalomenia g. n. ; 
Y. Macellomenia g. n. ; YI. Dondersia Hubrecht; VII. Nematomenia 
g. n. ; VIII. Myzomenia g. n. ; IX. Paramenia Pruvot ; X. Ismenia 
Pruvot ; XI. Lepidomenia Kowalewsky et Marion ; XII. Echinomenia 
g. n. Simroth attaches much importance to the fact that the Neo- 
meniidge are distributed between the littoral and the abyssal fauna. 
They avoid the surface region, keeping out of the reach of waves, 
whereas the Chitonidge are surf-animals with dorsal armature and broad 
suctorial soles. Pruvot’s discovery that Myzomenia banyidensis bears in 
its youth the dorsal plates of a Chiton shows that the Chiton-type is the 
more primitive. The passage of the Neomeniidee from the zone of 
rapidly moving water to quieter regions is supposed by Simroth to have 
been associated with the loss of protective shells, the narrowing and 
* Comptes Rendus, cxvii. (1893) pp. 59 and 60. 
t Conchologist, ii. 3 (1892) 4 pp. (sep. copy). 
X Zool. Anzeig., xvi. (1893) pp. 49 and 50. 
§ Zeitschr. f. wiss. Zool., lvi. (1893) pp. 310-27. 
