ON THE ANATOMY AND DEVELOPMENT OF PYROSOMA = 315: 
water into the sac-like body of the Pyrosoma; for the water passes 
out immediately, in a multitude of distinct jets, from the extremities 
of the tubercles. 
Lesueur next proceeds to describe the internal structure of the 
Pyrosoma. He mentions the internal and atrial tunics as one internal. 
tunic, and points out their distinctness from the external, except at 
the aperture and over those rounded lateral bodies, which I have 
much reason to think are renal organs. The branchial networks are 
recognized as such ; the endostyle is described as “un vaisseau replié 
sur lui-méme ;” the testis is noted, but is interpreted as the liver. 
The stomach is determined as such, while the intestine is regarded as 
the cesophagus ; and the cesophagus is considered to be the pylorus, 
opening into what Lesueur regards as the intestine—“ un canal assez 
large, glanduleux vers sa base” (p. 417), but which is, in reality, a 
sinus full of blood-corpuscles, 
__. The peripharyngeal ridge is accurately described as “ deux petits. 
filets qui vont en se courbant de chaque:cété,” &c. (p. 419); and the 
nature of the nervous ganglion is rightly determined. Pyvosoma is. 
classed among the compound organisms, and the foetuses are carefully 
though briefly noted. Lesueur confirms Péron’s statement concerning 
the rhythmical contractions exhibited by the whole body in the 
Pyrosomata. 
The figures which accompany this memioir are exceedingly good. 
I judge from them that Lesueur observed the atrial muscles, and that 
he has mentioned them as the line which separates the first zone of 
his transverse section (fig..13 4) from the second (p. 415); and again, 
in the description of the figures 5 & 6,as “les filets qui forment’ un 
réseau dont l’usage parait étre de lier les animaux du Pyrosome entre: 
eux.” In x, fig. 5, I imagine I recognize an ovisac. Lesueur de- 
scribes it as one of the ‘ceufs’ or foetuses, which are well represented 
in figs. 8-11. ae ae ; 
Contemporaneously with Lesueur,! that great, but unfortunate 
anatomist, Savigny, directed his attention to the Pyrosemata, the 
peculiarities of whose structure found, at length, an adequate ex- 
positor in him; and his account of the anatomy. of Pyrosoma 
giganteum is at. once so lucid and so concise, that I cannot do better 
than reproduce it, as an introduction to my own memoir. 
1 The second memoir of the second part of the celebrated .‘ Mémoires sur les Animaux 
sans Vertébres,’ entitled ‘* Observations sur ‘les ‘Alcyons a deux oscules apparens, sur les’ 
Botrylles, et sur les Pyrosomes,” bears the’ inscription, ‘‘Lues a la premiere classe de 
l'Institut le le" Mai 1815 ;” with the note, ‘‘Ce mémoire a été présenté le 17 Avril; mais. 
les travaux de la classe en ont fait différer la lecture.” 
