T6 REMARKS UPON APPENDICULARIA AND DOLIOLUM 



The posterior extremity is similarly produced into a short tube with 

 a thickened base, but the tube looks outwards, and its walls are very 

 delicate, and consist of fine fibres like those of the fin of Sagitta. 



9c. The body of the animal consists of two tunics, an inner and an 

 outer,! which surround a wide central respiratory cavity. 



Six muscular bands {f), pretty nearly equidistant, gird the inner 

 tunic. 



In some specimens a sort of shrivelled tubular process projects on 

 the dorsal surface posteriorly between the two last muscular bands. 

 Is this the remains of an earlier pedicle of attachment ? 



91. A tubular endostyle (f) lies in the dorsal sinus between the first 

 and third muscular bands. 



In the ventral sinus a round ganglion («) lies just in front of the 

 third muscular band. It gives off several long nerves, four of which 

 are especially remarkable, and run diagonally to the anterior and 

 posterior apertures. There is no auditory sac nor otolithes. 



92. The branchia; divide the respiratory cavity into an anterior and 

 a posterior chamber. They are formed by the epipharyngeal and 

 hypopharyngeal (.r) bands which stretch across the respiratory cavity, 

 supporting on each side a number of tubular bars {y). In the upper 

 and lower division of the branchiae, these bars are adherent to the 

 walls of the respiratory cavity, i.e. to the inner tunic, and there their 

 canals open into the lateral sinuses ; but in the middle part of the 

 branchis their extremities unite and form loops without adhering to 

 the inner tunic, merely lying against it. There is a free passage for 

 the water between the bars, and on each side of the central supporting 

 bands. 



The edges of the bars are richly ciliated, and the cilia of their oppo- 

 site sides move in opposite directions. 



Although it appeared quite certain that the canals of the bars com- 

 municated with the sinus system, yet no blood-corpuscles could be 

 traced into them. 



The branchial bars did not extend so far forward above as below. 

 In the former case they reach as far as the second muscular band 

 only, in the latter, beyond the first ; seen from above or below, the 

 branchia appeared as an oval plate, with a clear space down its middle 

 and transverse bars on each side. 



93. The mouth {g) opens in the middle of the upper division of the 



^ The outer tunic, which I consider as homologous with the test and outer tunic of the 

 Ascidian fused together, was found by MM. Lowig and Kolliker to contain ceUulose, whence 

 they concluded the Ascidian nature of the animal, a deduction strikingly confirmed by 

 anatomical investigation. 



