On the Nutrition of the Salpa Embryo. 369 



confluent, and becoming deeper beyond the middle ; beneath 

 sparsely pubescent, somewhat densely, moderately coarsely 

 punctured, the metasternum more finely punctured in the 

 middle. 



Length 12, breadth 4^ millim. 



Hah. N.E. Tasmania, Gould's Country. 



I have seen three specimens of this species : two recently 

 brought from Tasmania by Mr. J. J. Walker, late of H.M.S. 

 ' Penguin,' to whom they were given by Mr. A. Simson, of 

 Launceston, from one of which the above description is taken 

 (the other having been deposited by Mr. Walker in the British 

 Museum), and a third in Mr. F. Bates's collection. Mr. Bates's 

 specimen is lighter in colour, it being reddish brown, with 

 the broad marginal stripe of the elytra stramineous. 



Sept. 23, 189.3. 



LV. — On the Nutrition of the Salpa Embryo. 

 By W. K.Brooks*. 



As the mammalian placenta nourishes and aerates the blood 

 of the foetus by the diffusion of gases and food in solution 

 through the walls of the blood-vessels, it has been generally 

 taken for granted that the placenta of Salpa performs its 

 function in the same way; and it has been described as 

 divided into a foetal chamber and a maternal chamber, 

 although its cavity is in reality part of the body-cavity of the 

 chain- Salpa, and the blood which circulates in it that of the 

 chain-Salpa. The Salpa embryo is bathed by the water 

 which is constantly flowing past it, and it is therefore in very 

 much closer relation to the external world than a mammalian 

 embryo shut up in the interior of a large thick-walled body. 

 There does not seem to be any need in Salpa for a respiratory 

 placenta, and its thick spongy walls seem to indicate that it 

 is not respiratory. We find in its structure nothing like the 

 interlacing villi of the mammalian chorion, and the sections 

 show that the embryo is nourished in a way quite unlike 

 anything which has been described in the Mammalia. 



The subject is a very interesting one. The rapid growth 

 of the Saljm embryo is one of its most conspicuous charac- 

 teristics, and the nutrition which this rapid growth demands 



* From the ' Johns Hopkins University Circulars/ vol. xii, no. 106, 

 pp. 97, 98. 



