110 DR. J. STEPHENSON ON THE MORPHOLOGY, CLASSIFICATION, 



of the genital organs, but altliougli I had a numbei' of specimens, 

 including one in a very en-rly stage, I did not discover the testes 

 (" the testes seem to disappear early, and I could not distinguish 

 them in a specimen which showed sperm-morulfe in all stages of 

 development, but no other genital organs, male or female, except 

 the ovaries in an early stage"). 



Since that date I have again met with numbers of sexual 

 specimens of this species, and have always looked for the testes, 

 but have never found them, even in the earliest stages of 

 sexuality. On the contrary, careful examination of the Hving 

 animal (which is very transpai-ent), of stainefl specimens, and of 

 sections, have united to convince me that the male cells are 

 produced in various parts of the body ; and not only so- — their 

 production is not limited to the parent animal of the chain, but 

 is spread over the whole series of individuals, and occuis in the 

 youngest members of the chain, which are scarcely recognizable 

 as separate entities, as well as in the most advanced. 



The situations where the male cells arise are mainh'^ as 

 follows : — 



(1) On strands passing between the alimentary canal and 

 parietes. The genus as a whole, and certainly this species, is 

 remarkable for the incompleteness of the septa ; in this species 

 there is nowhere a definite diaphragm across the coelomic space ; 

 and many of the strands, in various parts of the animal, from 

 which some of the sexual cells arise, should no doubt be regarded 

 as representing septa. 



(2) On the inner surface of the body-wall, often in the angle 

 where one of these strands joins the parietes. 



(3) In the new cellular-tissue which is formed in abundance 

 as a ring round the body at the site of the future divisions of 

 the animal. This cellular tissue gives rise to a number of new 

 segments ; the region is hence called the budding zone, and the 

 production of this embryonic tissue is the first sign of subsequent 

 fission. 



I propose to select as an example for description one out of 

 numerous observations, and then to add some account of the 

 appearances in sections, concluding with a few general remarks. 

 I may say that I have been particularly alive to one (I think 

 the only) source of possible error — namely, that the testes might 

 be quite inconspicuous masses in the normal position, that the 

 sexual cells might be detached very early in their history, and 

 the developing morulse, wandering widely through the body, 

 become attached to the body- wall or to strands in various 

 regions, so simulating the production of morulse in these 

 situations. This would, a priori, not be impossible, for the 

 following reason : — There are, in this species, no sperm- sacs or 

 ovisacs, and this seems to depend on the incompleteness of the 

 septa, of certain of which the sacs, in other genera, are backward 

 protrusions ; the sexual products, instead of being received into 



