164 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
ducts, which are bounded by folds which project inwards. A large 
glandular duct formed of two applied folds extends from one extremity 
to the other, and divides the canal into two portions ; the duct on the 
right is both oviduct and deferent canal, that on the left is the vagina, 
which terminates inferiorly in a cul-de-sac with which the terminal 
reservoir is connected ; this is always filled with absolutely pure sperm. 
The external genital duct takes such a course as to make the vaginal 
orifice a special one, and this explains how it is that the animal which 
is playing the part of the female may be laying eggs at the same time 
that it has the penis of the male in the vagina. 
It would appear that the organs function thus : the sexual products 
reach the common chamber, where the ova are fertilized by the sperm 
collected during copulation in the seminal reservoir; here, too, they get 
albumen. The products then pass into the twisted and mucus glands. 
When the animal emits the sperm follows the groove which is continued 
all along the erected penis and is introduced into the vagina of the 
female. 
Glands of Aplysise.* — Sig. G. F. Mazzarelli describes the “ opaline ” 
or “grape-like,” and the branchial or mantle glands in A])lysise. In 
Aplysia limacina, the glandular cells of the gill-cover emit a violet 
liquid only, while the opaline gland produces a white, or a purple, or a 
mixed white and purple secretion. In A. depilans, the opaline gland 
usually emits a white liquid only ; the other gland produces the same, 
or plus a violet secretion. In A. punctata, the secretion of the opaline 
gland is white, or white and violet mixed, while that of the gill-cover 
gland is violet. There is thus no constancy in the origin of either 
liquid, nor has the observer discovered any reason why the secretion 
should be so variable. The secretion is protective, concealing the 
Aplysia in the exuded pigment, or disgusting enemies by the strong 
odour. 
5. Lamellibrancliiata. 
Nature of Byssus.f— Dr. E. Horst claims to have shown that the 
byssus-groove, in w^hich the byssus-filament is formed, is continued into 
the byssus-cavity, into the wall of which it gradually passes ; this cavity 
is, for its whole extent, surrounded by secreting gland-cells. When, 
therefore, a byssus-filament is formed, it is easy to understand that there 
is at the same time a secretion in the cavity, and in this cavity a lamella 
continuous with the byssus-filament is developed. As every successive 
lamella incloses its predecessor as in a sheath, and they all unite to 
form the byssus-stem, an increase in the number of byssus-filaments is 
connected with a growth in length and thickness of the byssus-trunk. 
Hinge of Pelecypods and its Development. J — Mr. W. H. Dali dis- 
cusses the characters and development of the hinge of the shell of Pele- 
cypods (more commonly known as Lamellibranchs), and attempts to form 
a better subdivision of the group than has been proposed hitherto. The 
author thinks that there can be but three fundamental types of hinge, 
* Zool. Anzeig., xii. (1889) pp. 580-3. 
t Tijdschr. Nederland. Dierk. Ver., ii. (1889) pp. 248-59 (1 pi.). 
t Amer. Journal of Science, xxxviii. (1889) pp. 445-62. 
