12 Moll 
MOLLUSCA. 
H. V. liiERiNG observes that the orifice of the genital organs is within 
the organ of Bojanus, or kidney, in the Ostracea, in Arca^ and in several 
Mytilaceaj but in some species of Mytilus, the orifices of both organs are 
on the same prominence, close to each other ; in Dreissena^ on the con- 
trary, Fectunculus and all Sinu^mlliata, except the Anatinidcej both 
orifices are independent. The author regards the former as the lower, the 
latter as the higher degree of organization. He supports DalPs statement 
that the products of the genital glands are evacuated in Patella by dehi- 
scence through the renal organ [Zool. Rec. xiii. Moll.^ p. 35] ; this is also 
the case in the left side of HaliotiSj whereas in Fissurella the genital 
orifice is inside the opening of the renal organ. Z. wiss. Zool. xxix. 
pp. 683-614, pi. XXXV. 
W. V. Natiiusius has published a work {supra, p. 6), in which he 
endeavours to prove that the shells of Mollusks do not grow only by 
apposition, but that an extension of the shelly substance by intus-suscep- 
tion must be admitted. For this purpose, he enters very minutely into 
the microscopic structure of the shells, especially -of Sfrombus gigas, 
pi. iv. figs. 21-26, and Mytilus edulis, pis. v.-xi. The chief points leading 
to this conclusion are apparently the following : — 
(1) The single prisms of the prismatic layer of a young Anodonta are 
smaller in diameter than those of an adult shell at the same absolute 
distance from the summits (p. 97). 
(2) The blue shelly layer in Mytilus edulis shows a distinct increase in 
thickness about the middle of the shells and another near the edge, 
in old and in young shells, but at the same absolute distance from the 
summits the thickness is different in old and young shells (p. 77). 
(3) The minute disposition of the same blue layer, the nacreous layer, 
the shelly ridges to which the ligament is attached and the outside cuticle, 
as shown by transverse sections in full-grown and young shells of Mytilus 
edulis (pi. viii. figs. 44 & 45), show differences which cannot be explained 
by simple apposition from within and erosion from without, but only by 
increase of the thickness of the blue layer. The author calls attention to 
the structure of the “ schlossbandwall,” or ligamental ridge {nymphce, 
Linne), which is perforated by five channels. 
A peculiar gland in connection with a hollow perforated sting within 
the orifice of the genital organs in Asteronotus, family has been 
described by R. Bergh, JB. mal. Ges. iv. p. 161. 
A peculiar horny sting connected with the penis and containing stellate 
cells, found in OncMdium,hy Semper, Arch. mikr. Anat. xiv. p. 123. 
Note on the hermaphroditical gland of Ampborina, by S. Trinchese, 
Mem. Acc. Bologn. (3) vii. p, 463. 
Embryology. 
E. R. Lankester supposes an original simple circle of ciha round the 
mouth which he calls “ architroch,'* as the common origin of the vibratory 
apparate of the Rotifera, the tentacular crown of the Polyzoa, the arms 
of the Brachiopoda, the oral appendages (palps) and gills of the Bivalves, 
which therefore all would bo morphologically homologous. Q. J. Micr. 
Sci. (2) xvii. pp. 423-428. 
