REPORT ON THE TUNICATA. 13 



Test gelatinous and transparent, containing no spicules, but many small cells. 

 Branchial Sac well developecl, not folded. Consisting of numerous transverse 



vessels separated by narrow slits (the stigmata), and numerous internal 



longitudinal bars. 

 Tentacles present ; simple. 

 Dorsal Lamina in the form of languets. 

 Alimentary Canal placed posteriorly to the branchial sac. 

 Reproductive Organs placed in the wall of the peribranchial cavity, posterior to 



the branchial sac. The embryo becomes a rudimentary larva (the cyatho- 



zooid), which gives rise to the first Ascidiozooids of the colony. 

 Gemmation takes place from a ventral and posterior stolon. 



This family, the only one yet known in the Ascidiae Salpiformes, corresponds 

 exactly to Savigny's family Luci^,' — a group which, although called a family by 

 Savigny, that author really regarded as being of much higher rank than we now under- 

 stand by a family, since he considered it equivalent in his system of classification to the 

 whole of the Simple and Compound Ascidians together. His family I. is " Tethy.^;," 

 and he divides that into two groups — (l) " Tdthyes Simples," the Simple Ascidians; 

 and (2) "Tethyes Composees," the Compound Ascidians; while his family II. is 

 " Luci^," the Pyrosomatidse, which thus ranks with what we now call an order. The 

 term Pyrosomatidte was first used, I believe, as a family designation by Prof T. R. Jones'' 

 in 1848. Its characters are naturally those of the suborder Ascidia3 Salpiformes, and 

 these will be discussed further under the heading of the single genus. 



Pyrosoma, P^ron. 

 Pyrosoma, Peron, Ann. d. !Mus., torn. iv. p. 437, 1804. 



Colony free-swimming, and having the form of a cylinder with a large central 

 cavity closed at one end and open at the other. 



Systems — only one present, the terminal aperture being the common cloacal 

 opening, and the central cavity the common cloaca. 



Ascidiozooids elongated antero-posteriorly, and placed in a single layer with their 

 anterior ends external and their posterior ends internal. Branchial aper- 

 tures anterior, opening on the surface of the colony. Atrial apertures 

 posterior, opening into the centrally placed common cloaca. Body not 

 divided externally into thorax and abdomen. Apertures not lobed. 



Test gelatinous and transparent, containing numerous stellate branched cells. 



Branchial Sac well developed, not folded, and not extending to the posterior 

 end of the body. Vessels of two kinds : transverse vessels, which are 



' Mcmoircs, p. 139. - In the article Tuiiicata in Todd's Cyclopscdia of Anatomy and Physiology. 



