ANATOMY AND PHYSIOLOGY. 
Moll 41 
10 » Embryology. 
A research on the early development of Sepia [cf. Zool. Rec. xxiv, Moll. 
pp. 28 & 39] is published in full, with illustrations ; Vialleton. 
Id the segmenting ovum of Loligo three zones are recognised — central, 
intermediate, and marginal. The second becomes by delamiuation two 
cells thick ; certain cells in it assume a spindle-shape, and are regarded as 
yolk-membrane hypoblast-cells, although they do not share in the forma- 
tion of the digestive tract ; Watase. 
The embryology of the Unionidoi has been followed, and is described in 
detail, with illustrations, until the shell has attained a leugth of about 
2 cm. ; ScilIERIIOLZ. 
Philine aperta lays its eggs in elongated masses on the sand! The 
vitellus, OT mm. in diameter, divides into two, then four, after which 
bilateral symmetry is apparent. Eight ectodermal cells gradually sur- 
round by epibolic division the four vitelliue cells. One ectodermal cell 
becomes clear, and divides into four, which are the primitive mesoderm. 
The blastopore is situated in the middle of the ventral surface ; it is slit- 
shaped, and the two sides meet, separating an anterior portion, the future 
mouth, and a posterior which becomes the sliell-gland. The velum and 
foot are formed in the usual way. The pedal ganglion arises from cells 
lying against the otocyst. There are no cephalic eyes, but a large lateral 
one, situated where the anus will afterwards appear. The endodermal 
cells form a cavity by division, which corresponds to the future liver, 
stomach, and intestine ; the mouth and anus are formed late. The 
external layer of the mesoderm, not growing so rapidly as the ectoderm, 
becomes vacuolated, and the cavities thus produced fuse together. In 
this way, and not by cleavage, the coelome is formed. There is a large 
columellar muscle, and also an operculum. The embryo at first swims, 
then sinks, owing to atrophy of the velum; Lacaze-Duthiers & 
Pruvot. 
Development of Limax agrestis ; Shalfeev’. 
Account of early stages of Chromodoris elegans ; Riio. 
Various stages, especially the later oues, of the oyster are described ; 
the names “ prodissoconch ” and “ dissoconch n are proposed for the larval 
and adult shells of Pelecypoda ; Jackson, R. T. (1). 
Young of Mytilus edidis often settle for a time on Gonothyrcea ; other 
occasional sites recorded ; McIntosh. 
11 . Phytogeny. 
The Pelecypoda have probably arisen from some such form as Nncula 
or Trigonia , and have diverged to the Ostrceidce in one direction, and to 
Aspergillum in the other ; Sharp. 
Phylogenetic arrangement of the Pelecypoda, as deduced from the 
structure of tho gills ; Pelseneer, (3) pp. 26, 27, & 37-40. 
Phylogeny of Cephalopoda ; Hyatt. 
The Vilrinidce are the ancestral group of a considerable number of the 
Pulmonata ; SlMROTH (1). Also id. (4). 
