NOTES ON JAPANESE TRICLADS. 447 



exceedingly rare, if at all, to discover individuals with developed sexual 

 organs. So far as my observations go, the fission ceases in the autumn 

 and then the reproductive organs begin to develop. It may therefore 

 be said, in unison with Curtis, 15 that the life history of those planarians 

 presents alternate periods of asexual and sexual reproduction. 



6. Budding. 



A very curious case of budding was observed in a specimen of 

 Sorocelis Sapporo Ij. et Kab., captured by Professor Ijima in the rivulet 

 flowing through the Sapporo college ground in Hokkaido. It is shown 

 in fig. 2. The mother individual is of quite normal appearance and 

 structure, possessing well-developed genital end-organs. Only it bears 

 on the left lateral body-margin in the pharyngeal region two branch- 

 like buds of considerable - dimensions. One of them represents an 

 additional posterior body-part and the other, an additional anterior 

 body-part. Both are structurally very distinctly differentiated. The 

 former contains developing pharynx and sexual end-organs, besides two 

 branch-bearing gut-trunks which are simply elongations of as many 

 lateral branches of the left posterior gut-trunk of the mother individual. 

 The latter may be said to represent nearly an entire young individual 

 organically connected to the mother individual by the tail-end ; the 

 eye-spots near the free truncate end number 5 or 7 on either side, 

 distributed in the usual way ; nearly in the middle there exists a well- 

 developed but as yet small pharynx ; two gut-branches originating from 

 the left posterior trunk of the mother individual enter into the bud as 

 the paired posterior gut-trunks of this ; these unite in front of the bud 

 pharynx, and from this point of union there arises an unpaired short 

 gut-trunk directed towards the head-end of the bud. A glance at the 



accompanying figure will make clear the relations of the supernumer- 



* 



ary parts or partial individuals to the mother individual. 



1) Curtis, W. C, 1902, The life history, the normal fission and the reproductive organs 

 of Planaria maculata. Proc. Boston Soc. Nat. Hist. Vol. XXX, No. 7, pp. 515-559. 



