ANATOMY AND PHYSIOLOGY. 
Moll . 17 
z. Inst. Wien, v. pt. 1. The absence of auditory organs in Chiton stated; 
id. ibid. 
Sensitive organs on the side of the foot along a furrow which begins 
behind the eye in the Scutibranchia , and compared with the lateral line 
of fishes ; B. Haller, Morph. JB. ix. pp. 1-98 ; abstract in J. R. Micr. 
Soc. (2) iii. p. 829. 
7 . Organs of Generation . 
Paired genital ducts in Nautilus ; Lankester & Bourne, Q. J. Micr. 
Sci. xxiii. p. 340. 
Some notes concerning the structure of the testicle and the formation 
of the spermatozoids in the Chitonidce ; J. F. van Bemmelen, Zool. Anz. 
1883, pp. 343, 344, & 361. 
P. P. C. Hoek elaborately describes the anatomy of the genital organs 
of the common oyster. After discussing the results and conclusions of 
previous authors, he gives the results of his own researches on individuals 
from the Oosterschelde, among which the following may be here men- 
tioned : — The genital gland is not a compact organ, but forms a number 
of anastomosing channels, which extend nearly over the whole main part 
of the body within the connective tissue below the surface ; the sperma- 
tozoids and eggs have their origin near each other in coecal appendages 
of these channels, probably both from the ectoderm, but not at the same 
time ; each egg is probably a transformed entire epithelial cell ; each 
mother-cell of a spermatozoid, however, is only part of an epithelial cell. 
The genital orifice is situated in a lateral slit of the anterior and inferior 
part of the body. The eggs are fecundated in the genital channels by 
spermatozoids originating from another individual, which have been carried 
by the water-currents not only into the mantle-cavity, but into the genital 
opening itself. Oysters, when two years old, are able to produce either 
eggs or spermatozoids, but their fecundity is greatest in their fourth or 
fifth year, and decreases afterwards, the liver increasing in size and en- 
croaching on the room occupied by the genital channels. During one 
season, nearly all the eggs of an individual are produced and hatched 
simultaneously ; the production of the spermatozoids follows that of the 
eggs in the same individual, and continues for some time ; aged indi- 
viduals produce some spermatozoids, but no eggs. Artificial breeding 
very probably exercises a disadvantageous influence on the fertility of the 
individuals. Tijdschr. Niederl. Dierk. Yer. Suppl. i. pp. 115-253 (in 
Dutch and French), pis. i.-v. ; abstract in Bull. U. S. Fish Comm. ii. 
p. 343, and in J. R. Micr. Soc. (2) iii. pp. 41, 354, & 355. 
J. A. Ryder confirms the opinion that the common European oyster 
is hermaphroditic, spermatozoids or eggs predominating at certain ages 
and seasons ; 0. virginiana and angulata , on the contrary, are monoecious 
or unisexual: Bull. U. S. Fish. Comm. ii. pp. 205-215. Bouchon- 
Brandely’s papers on the same subject [Zool. Rec. xix. Moll. p. 95] are 
translated ; l. c. pp. 319-341. 
Two kinds of spermatozoids observed in Paludina vivipara (as already 
stated by Yon Siebold and Leydig) and in Ampullaria, one hair-like, the 
