512 THE ANATOMY OF INVERTEBRATED ANIMALS. 



The endoderm of the pharynx is ciliated, and the cilia are 

 especially large over a narrow tract, or peripharyngeal band, 

 which encircles the oral aperture at the level of the anterior 

 end of the endostyle, and is continued back, as a liypoplia- 

 ryngeal band, along the middle of the neural face of the 

 pharynx to the oesophageal opening. 



On each side of the endostyle, the posterior part of the 

 hsemal wall of the pharynx presents two oval apertures or 

 stigmata (Fig. 147, d), encircled by cells, which are provided 

 with very long and active cilia. Each stigma leads into a 

 funnel-shaped atrial canal, the open end of which terminates 

 beside the rectum. 1 (Fig. 147, c.) 



The heart is a large sac, which exhibits rapid peristaltic 

 contractions, and is placed transversely between the two 

 lobes of the stomach. In the species which I observed no 

 blood-corpuscles could be seen, and the direction of the pul- 

 sations of the heart was not reversed at intervals, as it is in 

 the Ascidians in general. M. Fol, 2 however, states that, in 

 other Appendicular im, the reversal of the contractions of the 

 heart takes place. Like myself, he has been unable to dis- 

 cover any blood-corpuscles. There are no distinct vessels, 

 but the colorless fluid which takes the place of blood makes 

 its way through the interspaces between the ectoderm and 

 endoderm and the various viscera. 



The nervous system consists of a ganglion (Fig. 147, p) 

 situated nearly opposite the anterior end of the endostyle ; 

 in front, this gives off the nerves to the sides of the mouth, 

 while, behind, it is continued into a long cord (s), which runs 

 back beside the oesophagus, and between the lobes of the 

 stomach, to the base of the appendage. It then passes along 

 one side of the urochord to its extremity, giving off nerves 

 at intervals. At the origins of these nerves aggregations of 

 ganglionic cells are situated. (Fig. 147, t.) The most an- 

 terior of these ganglia is the largest. 3 



reality a longitudinal fold or diverticulum of the middle of the haemal wall of 

 the pharynx, which projects as a vertical ridge into the hfemal sinus, but re- 

 mains in free communication with the pharynx by a cleft upon its neural side." 



1 These stigmata were first described by Gegenbaur (" Bemerkungen Uber 

 die Organisation der Appendicularien," Zeitschrift fur wiss. Zoologie, 1855), 

 who supposed that they communicated with canals of the interior of the body. 

 However, by feeding Appendicularice with indigo, I demonstrated the commu- 

 nication of these stigmatic funnels with the exterior of the body. (Quarterly 

 Journal of Microscopical Science, I. c.) 



2 " Etudes sur les Appendiculaires," 1872. 



3 Quarterly Journal of Microscopical Science, 1856, pp. 8, 9. M. Fol, who 

 finds the same arrangement in other Appendicularias, counts this as the second 

 ganglion of the nervous system, and states that a fine canal traverses both the 

 ganglia and the longitudinal nerve. 



