Z AKT. 5. — T. AIDA. 



tematic of Appendicularia (Acaclemisch Proefschrift. Leiden, 1906) 

 has also remained out of my reach, and I greatly regret that 

 I have not been able to benefit by it. 



As my observations have been made on preserved specimens, 

 I am unable to give the description of the shape and structure 

 of the so called " Haus, " wliich is hardly preservable and can 

 thus be studied on the living animal only. 



Here I wish to express my hearty thanks to Prof. I. Ijima 

 of the Imperial University of Tokyo, under whose supervision 

 my investigation has been conducted, and to Prof. W. E. Rittee 

 of the University of California, who has favoured me with many 

 valuable sussestions. 



'öö^ 



Genus Kowalevskia. 



Kowalevskia tenuis Fol (1872). 



PI. I., figs. 1-4. 



Endostyle wanting. Dorsal and ventral wall of 

 branchial cavity have two rows of triangular plates 

 running from mouth to œsophagus. Atrial canal short; 

 its outer opening and spiracle are large, lenticular. 

 Mouth with a ring-form, unbroken lip. Branchial por- 

 tion of trunk strongly compressed dorso-ventrally and 

 sharply distinguishable from swollen gastro-genital re- 

 gion. AVith hood arising from the dorsal side of 

 gastro-genital region and covering anteriorly the dorsal 

 surface of branchial region. Oikoplastic epithelium 

 covering the dorsal side of branchial, and front side 

 of gastro-genital, region and forming at the lateral 



