14 
Emhryology of Saljpa. By W. K. BrooJcs. 
Salpa the sexes are distinct, and as the chain Salpa has no ovary the 
process of budding stops with the second generation ; while as the 
zooids of the other Tunicata are hermaphrodite the process may go 
on indefinitely. 
The history of Salpa is of especial interest, as it throws a great 
deal of light upon the manner in which separation of the sexes may 
be brought about in forms which were originally hermaphrodite, 
and it is also interesting to note that the elaeoblast, the history of the 
development of which shows it to be the homologue in the female 
of the testicle of the male, is concerned in reproduction, although it 
has lost all the characteristics of a sexual organ, and is simply a 
supply of food. 
We cannot fail to notice the connection between the manner in 
which the male Salpa is produced, and the numerous cases, through 
the various groups of the animal kingdom, in which the male is, to 
some extent, parasitic upon, or supplemental to, the female. 
The Cirrhipeds, Arachnids and the Argonaut, will at once suggest 
themselves, as familiar instances of the occurrence of such a relation 
between the sexes. 
These interesting theoretical points are simply mentioned here, 
as a more exhaustive discussion of them is reserved for another 
place. — A Paper read before the Boston Society of Natural 
History. 
EXPLANATION OF PLATE CXLIV. 
The small letters have the same signification throughout, 
a. Wall of branchial sac, j k. Atrial aperture, 
b. Wall of outer tunic. 
c. Sinus cavity. 
d. Branchial cavity. 
Egg. 
/. Opening of inner chamber of \ p. CEsophagus. 
placenta. I s. Stomach. 
g. Cavity of inner chamber of j t. Intestines. 
placenta. I n. Elseoblast. 
h. Cavity of outer chamber of ; v. Pericardium. 
placenta. i w. Inner tube of stolon. 
/. Branchial aperture. i x. Ovary. 
Fig. I. — Egg within the sinus system, and attached by a gubernaculum to 
wall of branchial sac, within the cavity of which a few spermatic filaments are 
seen. 
Figs. II., III., IV., and V.— Successive stages of segmentation. 
Fig. VI. — Gastrula within the brood-sac. 
Fig. VII.— Embryo, soon after the primitive digestive cavity has become 
divided into the branchial and placental chambers. 
Fig. VIII. — Embryo considerably advanced, showing the mid-atrium /, and 
one of the lateral atria m, which has already begun to split and form the muscles. 
Fig. IX. — Embryo at about the time that the stolon appears. 
Fig. X. — Stolon, at a very early stage, showing the ovaries x, x ; [in this Figure 
the letters a and b were accidentally transposed, so that b represents the outer 
tunic, and n the branchial sac]. 
I. Cavity of atrial chamber. 
m. Muscles. 
n. Ganglion. 
0. Nucleus. 
