314 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
south-eastern coast of the United States, to which are added illustrations 
of many of the species. The systematic conchologist will be glad to 
have this work. 
i8. Pteropoda. 
Cymbuliopsis Calceola.* — Mr. J. I. Peck gives an account of the 
anatomy and histology of this Pteropod, serial sections of which were 
made. The tentacles are, at best, mere knob-like structures with rudi- 
mentary sensory apparatus at their base. All the tissues of the animal 
are exceedingly translucent, so that the course of the oesophagus may be 
followed from a surface view. The visceral nucleus is dark brown and 
rounded, and contains the digestive and reproductive organs, while on 
its dorsal surface are laid the heart and nephridium. The primitive 
molluscan foot cannot be recognized in the adult, but its successor, the 
fin, has attained a very large size, and is moved by muscles which are 
laid in regular intercrossing bands a little beneath the epithelial 
surface of either side ; the thickness of the fin is due to the branching 
network of connective-tissue cells which is so characteristic of molluscan 
histology. The pallial cavity is on the ventral side, and is made by the 
large fold of the mantle which extends from the dorsal part of the 
animal beneath the fin, thickening between its two epithelial layers 
into the hyaline “casque.” Part of the inner layer of the mantle is 
specialized into the pallial gland or “ shield ” of thecosomatous 
pteropods. The genus seems to be typical of the family to which it 
belongs. 
y. Gastropoda. 
Anatomy and Histology of Renal Organs of Prosobranch 
Gastropods.! — M. R. Perrier has an extended memoir on this subject. 
The urinary apparatus of Prosobranchs primitively consists of two 
symmetrical organs identical in structure and function ; each consists 
of a sac, which communicates on the one hand with the pericardium, and 
on the other with the exterior. Absolute symmetry, however, is never 
seen in them. In the Diotocardia (with the exception of the Neritidas) 
and in the Heterocardia the organ of one side never communicates with 
that of the other ; their orifices, which are also always distinct, are 
situated at the tips of papillae which project into the mantle-cavity. 
Fissurella is the only Prosobranch which retains any of the primitive 
symmetry ; but the left organ is much reduced, and does not communi- 
cate with the pericardium. The two kidneys have the same function. 
In all the rest the right kidney is the true renal organ, while the left, 
which is remarkable for its plasticity, always undergoes modifications 
in position or constitution. In Patella the two kidneys have renal 
functions, but the left, which is quite small, lies between the pericardium 
and the right kidney, and it appears to have lost its communication with 
the pericardium. 
In the Heteronephridiata (Haliotis, Trochidse) the left kidney under- 
goes a complete change, being converted into the papillary sac. It 
seems to have become an important reserve-organ, which communicates 
* Stud. Biol. Lab. John Hopkins Univ., iv. (1890) pp, 335-53 (2 pis.). 
t Ann. Sci. Nat., viii. (1889) pp. 61-315 (9 pis.). 
