68 



TUNICATA APPENDICULARIAXS 



ducts merely breaking through to the exterior at the point 

 marked g.d in Fig. 30. The spermatozoa are generally matured 

 and shed before the ova, and thus self-fertilisation is prevented. 

 The ova are very small, and little is known of the develop- 

 ment. 



n.cTi. 



FIG. 30. Longitudinal optical section of Oikopleura. Part of the tail is cut off. a, 

 Anus ; at, atrial opening ; br.s, branchial sac ; c.f, ciliated funnel ; ec, ectoderm ; 

 end, endostyle ; ep.p, epipharyngeal ridge ; g.d, opening of gonads to exterior ; 

 M, heart ; hy.p, hypopharyngeal ridge ; i, intestine ; m, mouth ; mus, muscle- 

 bands in tail ; n, nerve-cord ; n', nerve in tail ; n.ch, urochord ; n.g, nerve- 

 ganglion ; n.g', ganglion in tail ; oes, oesophagus ; or.gl, oral gland ; ot, otocyst ; 

 ov, ovary ; sg, stigmata ; so, sense-organ ; sp, testis ; st, stomach ; t, test. (After 

 Herdman.) 



Classification. There are two Families of Larvacea : First, 

 the KOWALEVSKIIDAE, including only the remarkable genus 

 Kowalevskia, Fol, in which the heart and endostyle are absent, 

 and the branchial sac is provided with four rows of ciliated tooth- 

 like processes. The two known species have been found in the 

 Mediterranean and in the Atlantic. 



The second family APPENDICULARIIDAE comprises about eight 

 genera, amongst which may be mentioned: (1) Oikopleura, 

 Mertens, and (2) Appendicularia, Fol, in both of which the body 

 is short (1 or 2 mm. in length) and compact (Fig. 30), and the 

 tail relatively long, while the endostyle is straight. (3) Megulo- 

 cercus, Chun, from deep water in the Mediterranean ; M. abyssorum 

 is the largest Appendiculariaii known, having a total length of 



