92 THE VOYAGE OF H.M.S. CHALLENGER. 



depend. The hairs are not straight, but wavy, and appeared stifler than ordinary 

 cdia. This sense organ was not in sufficiently good preservation to allow of more 

 accurate histological investigation. A large nerve from the ganglion passed directly 

 ov^cr it in the middle line. 



" A pair of strong muscular masses is developed at the posterior part of the nucleus, 

 one mass lying on either side. These muscles appear to take origin from the under side 

 of the thickened horizontal membrane above, and to terminate on the sides of the 

 posterior part of the nucleus. The terminations of the muscular slips composing the 

 muscles are bifurcate (PI. X. fig. 3, m.h.). Other narrow transverse muscular bands 

 are present between the mouth and rectum, embracing the fore part of the nucleus 

 (PI. X. fig. 3, m.h.). The use or homologies of these muscles are not apparent. 



" The endostyle lies in the middle line, at the back of the nucleus, between the pair 

 of posterior muscles of the nucleus (PL X. fig. 3, en.). It is very short. It showed the 

 characteristic structure of the Ascidian endostyle — long, fine, granulated, spindle cells, 

 packed close side by side, with their long axes at right angles to the length of 

 the organ. 



" The relation of the endostyle to the horizontal membrane was not observed, since the 

 organ was only discovered after the nucleus had become detached from the membrane. 

 The endostyle was then found tucked in between the paired posterior muscles of the 

 nucleus. It is placed in the position given to it in the figures, because this seems to be 

 the necessarily correct one. The organ, at all events, is on the ventral side of the 

 animal, or on the side of the mouth opposite to that on which the nerve ganglion lies, 

 which is its normal seat. 



"The length of the base of the Ascidian was 5'5 cm., breadth 4v5 cm. ; extreme 

 length between tips of the protuberances 7 "5 cm. 



'•■ On the whole this very perplexing animal appears to be an Ascidian, in which the 

 respiratory sac is flattened out so as to become nearly horizontal, and in which no gill 

 network is present. In Cystingia (Bronn, Kl. und Ord. ii. p. 131) a gill network 

 cannot be disting;uished. 



"Tlie radial muscles belong to the longitudinal set of other Ascidians and are 

 internal ; the circular are external in relative position. I can find no homologues 

 of the muscles of the nucleus. In having the viscera contracted into so small a 

 nucleus, the animal resembles Salpa. The nerve ganglion is abnormal in position, 

 in being situate on the nucleus. It nevertheless is normal, in lying between mouth 

 and anus, whilst the endostyle is on the opposite side of the mouth, as in other 

 Ascidians. 



"The name Octacncmus hythw.s is proposed for this curious eight-rayed deep- 

 sea form." 



Professor Moseley expresses his views as to the structure of this animal in 



