286 



AKIRA IZUKA : 



" trephine " of 10 crenulations. The oesophagus is surrounded with 10 

 glands of a somewhat wavy outline, opening near its anterior end. Some 

 of their blind hind ends extend back a short distance over the proventri- 

 culus. The proventriculus is somewhat fusiform extending through the 

 segments XXIII — XLV, with a transverse diameter equal to about one- 

 third the breadth of body in the region containing it. The radial muscle 

 columns are very large, their height being nearly equal to the inner dia- 

 meter of the proventricular tube. The part of the alimentary canal posterior 

 to the proventriculus shows extensive paired and segmental diverticula. 



The posterior extremity (Fig. 3) is capable of producing successive 

 crops of collateral sexual buds. Each bud shows an external structure 

 similar to that of the mother individual and is provided with a pair of long 

 and annulated anal cirri. 



The tail buds, or the sexual zooids, 14 in number, present various 

 stages of development. They form a cluster attached to the ventral aspect 

 of the posterior end. As regards arrangement, they are in no way sym- 

 metrically disposed Of all of them, only three have reached an advanced 

 stage of development, though the eyes are observable in at least seven. 

 Seen from the ventral side the cluster shows an interesting feature (Fig. 3) 



in that at its base 



and in the median 



line it includes three 



buds which as yet 

 show no segmenta- 

 tion but are each 

 provided with two 

 distal processes, the 

 " Anlagen " of anal 



cirri. 



better developed 

 sexual buds is re- 

 presented in Fig. 



One of the 



Fig. 3. Posterior extremity of T. misakiensis, with a cluster of 

 sexual buds. Ventral view. 20/1 natural size. 



