ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
163 
of hook-like teeth in each row on the I’cadula. Dr. Boas is not certain 
as to what members of the Tectibranchiata most resemble this group of 
‘‘ Pteropocls ” ; the resemblance presented by Gastroptei'on may only be 
analogical. 
The thecosomatons Pteropods have a very wide area of distribution, 
l)iit may be separated into three groups: a small one found in cold 
northern waters, one limited to the temperate (and ? cold) seas of the 
south, while most of the species are found in all warm tropical and 
temperate seas in such a way that each species has its own northern and 
southern limit. Less is certainly known as to the geographical distribu- 
tion of the Gymnosomata, but some sjiecies are very widely spread ; in 
general their chorological characters appear to be similar to those of 
the Thecosomata. 
y. G-astropoda. 
A Heteropod in British Waters."^ — Prof. W. 0 . MTntosh, by re- 
cording the capture of an Atlanta in St. Andrews Bay, has informed us of 
the presence of an example of a group of Molluscs formerly unknown in 
British seas. Hitherto they have been considered characteristic of the 
pelagic fauna of more genial waters. All recent investigations, however, 
tend to enlarge the area of truly pelagic types, and to raise the question 
whether temj)erature alone is the cause of the appearance in and dis- 
appearance from our seas of such types. Temperature certainly seems 
to have a marked effect on the vertical distribution of certain types and 
of the pelagic ova of fishes ; but in the present case the influence of 
currents is probably of greater importance. 
Reproductive Apparatus of Aplysise.f — M. E. Robert finds that 
this apparatus consists of five parts : the hermaphrodite gonad, the 
eflerent duct, a complex organ to which he gives the general name of 
annexed genital mass, the common genital canal which opens on the 
right and in front of the gill, and the external genital groove. In the 
annexed mass the spermatozoa and ova become separated, and the latter 
are fertilized ; albumen becomes added to the eggs, and shells are 
formed, each of which contains some scores of eggs, connected with one 
another and forming a continuous band arranged in heliciform shape, 
with closely approximated whorls ; around these masses a cylindrical 
gelatinous sheath is formed. The eflerent canal penetrates into the 
interior of the mass and opens into a cavity, which is a kind of vestibule 
or common chamber which communicates with several other organs. 
The albumen gland, which opens into this chamber, is hidden by the 
neighbouring parts, and can only be seen in the upper right region. To 
the left the common chamber is continuous with a glandular organ, 
which receives the name of “ glande contournee ” ; its glandular walls 
are folded in such a way as to divide its cavity into a large number of 
small alveoli. The mucus-gland is formed by a very long hollow ribbon, 
provided in its interior with a double row of glandular lamellae, between 
which there is a cavity. The common genital canal extends from the 
annexed mass to the genital orifice; it is divided into several special 
* Ann. and Mag. Nat. Hist., v. (1890) pp. 47-8. 
t Collides Renclu.s, cix. (1889) pp. 917-9. 
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