TUNICATA. 
Moll. 65 
Salp^. 
W. K. Brooks describes the development of Salpa, and comes to 
the following conclusions : the solitary Salpa is female ; it produces a 
chain of males by budding, and discharges an egg into the body of each 
of them before birth ; these eggs are impregnated while the zooids of the 
chain are very small and sexually immature (there is no close inter- 
breeding), and develop into females, which afterwards produce other 
males in the same way. After the foetus has been discharged from the 
body of the male, the latter grows up, becomes sexually niature, and 
discharges its spermatic fluid into the water, to fertilize the eggs carried 
by other immature chains. Since both forms are the offspring of the 
female, the one by budding, and the other by true sexual reproduction, 
we have not here an instance of alternation of generations, but a very 
remarkable difference in the form and mode of origin of the sexes. 
Salpa takes the “ tadpole larva ” stage because the adult animal is loco- 
motive. The gill is not a rudimentary, but a specialized form of the 
branchial sac, no branchial slits being ever formed upon the sides of the 
sac, and the lateral atria becoming converted into the respiratory muscle 
girdles. The structure of the ganglion and sense organs is also much 
more specialized in Salpa than in the fixed Ascidians, and resembles 
that of their locomotive larvaa. The presence of the placenta is a mere 
analogy with the Mammalia^ since the resemblance is simply functional, 
and not morphological. Regarding the existence of a communication 
between the body cavity of the nurse and the inner chamber of the placenta, 
the author states that in all stages, from the first appearance of the cavity 
of the gastrula until the embryo is fully formed, the blood of the nurse 
can be seen passing into and out of the cavity of the placenta. Finally, 
the SalpcB are to be regarded as Tunicata specialized for permanent 
locomotive life. The fertilization of the eggs within the body of zooids, 
produced by budding from the same female, is not peculiar to Salpa, 
but is also observed in Pyrosoma and in several compound Ascidice, and 
probably will be found in most Tunicata. Todaro’s memoir on the 
same subject [see Zool. Rec. xii. p. 210] reached the author after he had 
finished his own account ; the discrepancies may partly, perhaps, be due 
to the circumstance that Todaro worked almost entirely upon sections of 
specimens hardened and treated with reagents, while the author made 
no sections, but confined his attention to the living animal. Bull. Mus. 
C. Z. iii. Nos. 11-14, pp. 291-348, with several woodcuts. [It is true 
that the accounts of Todaro and of Brooks are at variance regarding 
several important points, but they coincide in the main conclusion that 
the solitary and the chain-forming individuals are not the offspring of 
one another, but elder and younger progeny of the same parent.] 
W. Salensky has published an extensive paper on the embryonal 
development of Salpa democratica (Forsk.), describing the origin and 
transformation of each single organ ; he comes finally to the conclusion 
that Salpa is not morphologically allied to the Mollusca. Z. wiss. Zool. 
xxvii. pp. 179-237, pis. xiv.-xvi. 
