588 
MR. HUXLEY ON THE ANATOMY OF SALPA AND PYROSOMA. 
generative duct in the Botryllidee, it would seem that the ova make their exit in the 
same way as in the Salpce. 
All the Tunicata possess the power of gemmation, and the buds are always formed 
as in Salpa (though not always with the same regularity), from a diverticulum of 
the sinus system, 
65. With regard to the “ endostyle,” which appears hitherto to have been strangely 
confounded with the dorsal folds of the inner tunic, the writer can speak positively 
as to its existence in the Salpce, Pyrosomata and certain Botryllidee. In all these 
species it is figured by Cuvier, Chamisso, Savigny and Milne -Edwards*, but not 
described ; and as a precisely similar structure is figured by Savigny and others in 
the solitary Ascidians, it is not perhaps too much to assume that the endostyle exists 
in them also. Should such be the case, we should be furnished with a new and very 
remarkable distinctive character of the Tunicata\, 
The eleeoblast” of the Salpce appears to be represented in the solitary Ascidians 
by the calcareous mass in contact with the heart, described by Van Beneden in 
Cynthia ampiilloides. 
66. The simple epipharyngeal and hypopharyngeal bands of the Salpa have been 
traced through their first degree of complication in Doliolum to Pyrosoma and 
Botryllus, where they form a true branchial sac, differing from that of the simple 
Ascidians only in the number and size of its meshes. 
On the other hand, in Pelonaia the hypopharyngeal band itself has disappeared. 
It is a Salpa in which the oral and cloacal orifices have approximated while the “ gill” 
has become obliterated :|:. 
In the strange form Appendicularia (79.), the simplification is carried a step further, 
for there is but one orifice, the oral. The anus opens on the dorsal surface, and a 
long appendage is added in the same position as that of Boltenia, but instead of 
being a long pedicle of attachment, it is a free and energetically moving fin. 
67. To sum up what has been said, it appears that the Salpce are not, as has been 
generally supposed, an aberrant form of the Tunicata, but rather that they are con- 
nected by insensible gradations with the other forms of the group ; neither is there 
any circumstance in their two modes of multiplication at all at variance with what 
takes place in other genera of the family. 
The distinction between monochitonidous and dichitonidous Tunicata cannot be 
kept up in its present sense, for the proper inner and outer tunics are equally adhe- 
rent in all Tunicata ; and as expressing the degree of adherence of the test to the 
* Lister, in his description of Perophora, loc. cit., figures the endostyle and says, “ along the middle of the 
back is a vertical compound stripe, d (fig. 4), that seemed to me cartilaginous.” 
t Since the above was written the author has had the satisfaction of finding both the endostyle and the 
ciliated sac, in a small, very transparent Cynthia ( ? sp.) obtained at Felixstow', on the Sufifolk coast. 
X Clwlyosoma would appear to resemble Pelonaia in the absence of any distinct branchial sac ; but Escheicht’s 
figures are not very clear. 
