520 
SUMMARY OF CURRENT RESEARCHES RELATING- TO 
common rudiment of the dorsal tube and nerve ganglion arises as a 
solid string of mesenchyme cells, which are closely applied to the outer 
surface of the inner vesicle, a little to the left of the median dorsal line. 
The cord acquires a lumen, which later on communicates with the 
pharynx. When the rotation is completed the dorsal tube lies in its 
definite position in the median line. The nerve ganglion is constricted 
off from the dorsal wall of this tube. Mr. Lefevre’s study of Botryllus 
is in complete agreement with Hjort’s description of the bud-development 
of this genus, so that scarcely a word needs to be added. Pizon’s state- 
ment that the constriction of the ganglion from the dorsal tube cannot 
be established is directly contradicted. 
INVERTEBRATA. 
Locomotion of Invertebrates.* — Prof. C. Stewart devoted his presi- 
dential address for the year 1894 to an interesting account of the various 
organs and structures which are concerned in the locomotion of various 
marine Invertebrates. The method which he adopted in making his 
investigations was to very carefully fix the attention solely on one pair 
of limbs of a crab at a time, and by this means it was possible in the 
majority of cases to see what the rhythm was. A detailed account is 
given of the movements of the common shore-crab and of some of its 
allies. The address deals also with the movements of the hermit crab 
and with that of some Mollusca. 
Mollusca. 
Mollusca of the Bay of Bengal.! — Mr. E. A. Smith has a report 
on the Mollusca dredged by the ‘ Investigator * in the Bay of Bengal 
and the Arabian Sea in 1893 and 1894. He reports that the collection 
contains several very remarkable new forms, among which perhaps the 
genus Pontiothauma is worthy of special notice. This genus, of which 
an anatomical account will later on be published, appears to be allied to 
the Pleurotomatidae. Its enormously expanded rostrum, with the 
absence of eyes, radula, and operculum, at once separate this genus from 
any which it approaches in shell characters. It should be added that 
of the two species one has eyes. The occurrence of the characteristically 
Japanese Banella perca in the Indian Ocean, and the discovery of a 
British Lucina and an Atlantic Poromya are of great interest. Another 
instance of* wide distribution is afforded by Solenomya patagonica. 
a. Cephalopoda. 
Sexual Dimorphism in Nautilus.! — M. A. Vayssiere has an inter- 
esting note on the sexual differences exhibited by this Mollusc. The 
opening of the shell is seen to be in some cases ovoid and conical, and 
in others elliptical. Observations show that all the individuals with a 
wide orifice to the shell are males, while those in which the opening is 
* Proc. Linn. Soc. Lond., 1893-4 (1895) pp. 14-23. 
t Ann. and Mag. Nat. Hist., xvi. (1895) pp. 1-19 (2 pis.), 
j Comptes Kendus, cxx. (1895) pp. 1431-4. 
