532 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
two ectodermic regions are afterwards added. Originally the visceral 
coil lies in the mantle over the foot. Heart and kidney have a common 
ectodermic Anlage. The blood-vessels arise directly from lymph-spaces 
in the body. 
Convergence in Gastropod Shells.* — Dr. Grafin Maria von Linden 
maintains that there are but a few fundamental forms of Gastropod 
shell, and that similar forms recur in ui allied groups. She gives evi- 
dence of “ liomoogenesis ” or convergence in Melaniidse, Pleurotomidm, 
Cancellarikhe, Rissoidse, and Columbellidse. Almost identical forms 
may arise in groups which are at most very distantly related. 
Development of Acmaea.f — M. Louis Boutan has studied the hitherto 
unknown development of Acmsea virginea , one of the intermediate forms 
connecting cyclobranch Docoglossa, like the limpet, with the Rhipido- 
glossa. Although resembling Patella , it has a cervical gill like the 
Rhipidoglossa. The eggs are laid in April and May, and are scattered 
in the water. The author followed the whole development, but he 
restricts himself in this note to a notice of two important points : — 
(a) The torsion of the visceral mass cannot have to do with the twisting 
of the shell, for the shell is symmetrical ; it depends on the development 
of the foot. ( b ) The position of the terminal peak in patelliform shells, 
turned backwards in Emarginula , forwards in Acmsea, is immaterial ; 
whatever be the position of the peak, the animal always has the same 
relative position in the shell. 
Structure of Pleurotomaria.J — MM. E. L. Bouvier and H. Fischer 
continue their account of Pleurotomaria Quoyana , describing the nervous 
system, sense-organs, and radula. The results bear out the conclusion 
previously arrived at, that this is a primitive type. 
5. Lamellibranchiata- 
Structure of Nuculidse.§ — Dr. W. Stempell gives a detailed account 
of Leda sulculaia Gould and Malletia chilensis Des Moulins, two Chilian 
forms whose structure has hitherto been undescribed. They are among 
the most primitive of living bivalves, as is suggested on palaeontological 
grounds, and by the following anatomical facts: — the simple relations 
between shell and body, the primitive nature of the shell (e. g. absence 
of prismatic layer), the presence of a creeping sole and the slight de- 
velopment of the byssus apparatus, the simple structure of the feather- 
like gills, the primitive nature of the kidney, the fact that the gonads 
are sometimes in connection with the pericardium, the more or less 
separate pleural ganglia, the persistence of the otocyst duct, and the 
marked difference between nearly related species. In short, though 
true Lamellibranchs, the Nuculidae are phylogenetically near the base 
of the stem which diverged very early from the main Molluscan stock. 
Arthropoda. 
a. Insecta. 
Wings of Insects.)) — Messrs. J. H. Comstock and J. G. Needham 
devote the third chapter of their studies on wings to a discussion of 
* Zeitschr. f. wiss. Zool., lxiii. (1898) pp. 708-28 (2 pis.). 
t Comptes Rendus, cxxvi. (1898) pp. 1887-9. % Tom. cit., PP- 1361-3. 
§ Fauna Chilensis, ii., Supplement iv. Zool. Jalirb., 1898, pp. 339-430 (4 pis.). 
|| Amer. Nat., xxxii. (1898) pp. 230-57 (24 figs.), 335-40 (9 figs.). Cf. this 
Journal, ante , p. 190. 
