APPENDICULAIUA OF JAPANESE WATERS. 21 



The Inst two species, Oikopleura dioica and rufescens, make 

 up ;i well circimiscribctl i^ioiip within the genus O'lhopleura. 

 Dr. LoHMANN recognizes them as a group characterized essentially 

 by the possession of a buccal gland, b}^ the genitd glands not 

 extending over the lateral side of the alimentary canal, and by 

 the absence of the blind-sac of the left stomach. Besides, 

 there exists between the two species another common character 

 which was not mentioned by him, viz., the presence of a small diver- 

 ticulum on the right stomach lobe. As none of other known 

 species of Oikopleara liave this blind sac, it may be denoted as 

 an important character of the small group in question. 



Genus Stegosoma. 



Stcfßosoina mügnuni Langhs. (1880.). 

 PI. IV., figs. 12-17. 



Stomach separated into two portions, left and 

 right. Left portion large, connected to the right by a 

 very narrow and short tube. Œsophagus opens at this 

 connecting portion. Genital glands flat and thin, 

 covering the upper and lower sides of alimentary canal. 

 Ovary single; testis paired. Tail ^vith narrow mus- 

 culature and with a row of subchordal cells to the 

 right of chorda. 



The trunk is elongate and laterally compressed. The oiko- 

 plast epitheliun covers only the branchial region and the entire 

 alimentary canal is free from it (fig. 10, PI. lA^). The buccal 

 gland is small. The Eisen's oikoplast is well developed. The 



