NKW ASEXUAL TAl'EWOllM. 837 



parent, though (as the nari'ow stalk shows) just i-eacly for detach- 

 ment, a tube of the structure of the outer layer of the body 

 which traverses in a straight line nearly the whole of the body, 

 which opens into the bladder behind and has two segmentally- 

 ai-ranged orifices of communication with the external world. 

 There is no obvious answer to the question as to its nature. In 

 buds within the cyst of Eclmiococcus * a cavity is formed which 

 is not an ingrowth of the cavity of the whole cyst, but which 

 is alleged to be continuous up to the scolex. This, however, 

 has been denied and the scolex asserted to be entirely solid. But 

 even supposing a comparison is possible on the grounds that 

 the scolex of Echinococcus is hollow, the short tubes leading to 

 the exterior in the wonii of which the present paper contains 

 an account would seem to invalidate it. And, moreover, the 

 structure of this problematical tube is" not that of the bladder 

 with whicli it communicates. It seems, indeed, to be a special 

 structure and not a space connected in any way (or, rather, any 

 direct way) with an evagination of the scolex. 



For the greater part of the body I could only find a nerve-cord 

 on one side, where it was quite as obvious as in the "adult " worm. 

 In the anterior region, however, the nerve-cord of the opposite 

 side was visible for a short space. It was, however, not half the 

 size of its fellow, though of precisely the same structure and 

 equally unmistakable as a nerve-cord. Both cords lie in the 

 medullary region just at its bordering on the cortical layer. I could 

 find no enlargement of the nature of a brain. Quite anteriorly, as 

 well as posteriorly in the bladder region, I could not recognise a 

 nerve-cord. It is noteworthy that the asymmetry of the two 

 water vascular tubes in size is exactly paralleled by that of the 

 two nerve -cords. 



These are the facts which I have ascertained in the anatomy of 

 the most mature of the growing buds. It now remains to compare 

 the structure of the young worm with that of the parent stock of 

 which it is a bud. 



§ ComiKcrison of Bad vnth Parent Worm. 



In the general form of the body and in the possession of a 

 relatively small bladder they agree ; also the rudimentary scolex 

 is a marked feature of both young and old. 



It is rather remai^kable to find asymmetiy in the young 

 worm, but this of course may be its normal method of growth. 

 Cei'tainly I noticed no asymmetry in the parent form. What 

 is perhaps important as a difierence is the presence of only two 

 water vascular tubes in tlie yoving and four of these in the 

 older worm. The additionn.l water vascular tubes may, however, 

 make their appearance later. Furthermore, for the same 

 reason, too much stress cannot be laid upon the more copious 



* Bronn's Thierreichs, iv. Abtli. 1b, p. 1549. 

 Proc. Zool. Soc— 1912, No. LYI. 56 



