18 Moll. 
MOLLUSC A. 
regarded by the author as very probably erroneous. The velum really 
exists in the embryo of the Limnmdce, as first stated by Ray Lankester. 
The organ called “ shell-gland ” by Ray Lankester and “ tube rectal ” by 
Lereboullet, is rudimentary, and its physiological function is not known. 
The primordial kidneys, first seen in the Limncaidoi by Stiebel, and first 
correctly described by Biitschli, are formed of perforated cells, and are 
really homologous to the segmental organs of the Annelida^ as stated by 
Fol in 1875. The embryos of Gastropods belonging to very different 
Orders and Sub-orders are very often quite similar ; for instance, those of 
Limncea and Torgipes^ Planorhis and Bithynia^ Hyalo^a and Firoloidea. 
The nervous system really originates from the ectoderm, as in other 
animals, although Bobretzky states the contrary ; the definite kidney 
originates from the mesoderm, though all former observers derive it 
from the ectoderm. The first appearance of lateral asymmetry in the 
embryo and its further consequences, are discussed at large. Morph. JB. 
V. pp. 662-660, pis. xxxii.-xxxviii. 
The changes before segmentation in the egg of Helix aspersa observed 
by J. Perez, J. de TAnat. Phys. xv. pp. 329-401, 2 pis. ; abstract in Rev. 
Int. iii. p 280, and in J. R. Micr. Soc. ii. pp. 405 & 834-836. 
L. Mark publishes a summary account of his’ observations on the early 
development of Limax campestris (Say), Zool. Anz. ii. pp. 493-496 ; 
W. Mayzel, some on the nucleus of the egg-cells in Limax variegatus 
(Dr.), 1. c. p. 282. 
O VO- viviparity of Helix studeriana, inaiqualis, and Partula stated by 
Viguier, O. R. Ixxxix. pp. 866-868. [This already observed by Dufo, 
Ann. Sc. Nat. xiv. 1840, and H. Crosse, Nachr. mal. Ges. i. 1869, p. 4.] 
Development of Urosalpinx cinerea and [^Columhella'] Astyris lunata, 
from the segmentation of the egg to the hatching, by W. H. Brooks, 
Chesapeake Zool. Laborat. 1878, pp. 121-142, pi. viii. 
On development of Chiton ^ by Kowalewsky, supra. 
S. LovkN has published in German {supra) his observations on the 
development of several Bivalves, chiefly Modiolaria marmorata (Forbes), 
Cardium exiguum (Gmel.), Montacuta ferruginosa and hidentata (Mont.), 
and Mytilus edulis (L.), with the original figures; these appeared first in 
Sv. Ak. Handl. 1848, in Swedish. 
W. H. Brooks gives a preliminary abstract of his observations on the 
development of Ostrea virginiana ; Zool. Anz. ii. pp. 659 & 660. 
Note on the embryology of Mytilus edulis by T. Barrois; Bull. Sci. 
Nord. (2) ii. pp. 137-146, 1 pi. On that of Pholas ; id. Assoc. Franc, vii. 
(Nantes) p. 302. 
11 . Biology. 
O. Nusslin has made numerous experiments on the evaporation of 
fluids of land-shells, and on their power of re -absorption of water from 
without ; he comes to the conclusions that if slugs are exposed to dry- 
ness, the evaporation is greatest at the beginning and eventually dimi- 
nishes ; about 87 per cent, of their weight in a normal state is water, 
and they perish when they have lost about 17 per cent, of their own 
