I 
246 POPULAR SCIENCE REVIE'^V. 
parent tubes, which may perform the function of a liver, or 
represent a rudimentary absorbent system. ; 
Though the circulatory system consists of “ sinuses,” i. e., i 
blood-channels without distinct walls, many of these are con- 
stant in position ; namely, the dorsal^ enclosing the endostyle ; 
the ventral, in which the ganglion lies — lateral sinuses connect- 
ing the two former — a sinus surrounding the viscera, and a 
channel which traverses the “ gill.” These communicate round 
the oesophagus ; above and in front of which lies the heart (fig. , 
11, h ) — an imperfectly tubular organ, having walls of stripped 
muscular tissue. There is a blood-tide, with intervening pause, 
as in the Ascidia. 
It had long been noticed by naturalists that the Salpido3 oc- 
curred in two well-marked forms ; one, as a solitary specimen ; 
the other consisting of a number of individuals joined together 
in a chain, which moved through the waters of the ocean in a 
serpent-like course. These two forms were described as distinct 
species until Chamisso discovered that they were but phases in 
the existence of one and the same zoological individual. 
It will be advisable to term them, after Huxley, “ Salpa A,” 
and Salpa B,” in order to avoid the use of a theoretical 
nomenclature. ■ 
Though these forms are ver}^ similar internall}^, they differ 
outwardly in certain points, such as shape, texture of the inte- 
gument, number of the muscular bands, and length of the en- ^ 
dostyle. Pincircling the nucleus of a specimen of Salpa A, may 
often be found a cliain of embryonic B Salpce, which are at- : 
tached in pairs to the side of a cylindrical tube which takes j 
origin just in front of the heart, and is an outgrowth from the i 
sinus-system. The cavity of this ‘‘gemmiferous tube” com- S 
municates with the dorsal sinus of each embryo ; and Professor I 
Huxley “has seen one of the large blood-corpuscles of the I 
parent entangled in the heart (which was not more than | 
of an inch long) of a very young foetus.” I 
Each embryo is attached to its neighbour by means of a com- I 
municating channel bet\yeen their sinus systems. This channel ^ 
gradually narrows until it becomes a mere pedicle ; and, finally, J 
all communication ceasing, the young S(dpa B is free. > 
“It is clear, therefore,” says Professor Huxley, “that the 
gemmiferous tube is nothing more than a stolon, containing a 
diverticulum of the circulating system of the parent, and the 
whole process of reproduction as it is manifested in Salpa is 
one of gemmation. Salpa B is a bud of Salpa A.” Before its 
liberation from the chain, each B Salpa generally contains a 
Holitanj fcetus, attached by a pedicle to the upper and hinder ^ 
part of the wall of its respiratory cavity. This connection be- h 
tween parent and offspring is, moreover — most wonderful to re- g 
