44;) 



CHORDATA 



Cviitliia* MOLGULID-, oral opening, six-lobed, atrial four-lobed. Molgula* 

 Kni;\ra* Sub Order II. SYNASCIDL3E. Compound ascidians consisting 

 of numerous small individuals imbedded in a common tunic. Usually (fig. 502) 

 the individuals of a colony are divided into small groups, the oral openings of a 

 group forming a rosette around a common central atrium. Distaplia,* Lepto- 



FiG. 500. Development of an Ascidian (after Kupffer and Kowalevsky). i, 

 larva, just hatched; 2, cross-section through the tail of a slightly younger larva; 3, much 

 younger stage, formation of notochord and nervous system; 4, anterior end of a larva 

 just before attachment. (2, Phallusia mentula; 3, 4, Ph. mammillata.) au, eye; c, 

 notochord; cl, tunic; d, digestive tract; d', its nutritive, d", its respiratory division; e, 

 atrial vesicle; ek, ectoderm; en, entoderm; h, brain; i, oral invagination; m, muscles of 

 tail; n, neural tube; ne, neurenteric canal; o, otocyst; p, adhesive processes. 



.4 



B 



FIG. 501. FIG. 502. 



FIG. 501. A. Molgula manhattensis*; B, Eugyra pillularis* (from Verrill). 

 FIG. 502. Botryllus violaceux (after Carpenter). .4, small colony of eighteen 

 individual groups; B, two inaividual groups somewhat enlarged. 



clinum* Polyclinum* Amaroudum* Botryllus* Sub Order III. LUCI/E. 

 Free-swimming pelagic synascidians, having the form of a hollow cylinder closed 

 at one end; the animals vertical to the axis of the cylinder, oral apertures on 

 the outside, atrial in the central cavity. Pyrosoma, very phosphorescent, 

 tropical, some species four feet long. 



