THE STRUCTURE AND AFFINITIES OF HERDMANIA CLAVIFORMIS. 249 



is on the basis of Uljanin's ('84, p. 93) interpretation of the ventral stolon of Doliolum. 

 This investigator finds seven strands of cells in the stolon, all within a common ecto- 

 dermal envelope. On one side there is a large unpaired strand which gives rise to 

 the central nervous system; under this, occupying the centre of the stolon, another 

 unpaired mass gives rise to the pharynx and intestinal tract. Beneath this there 

 is still another unpaired strand from which the pericardium and heart take origin. 

 In addition there are two pairs of lateral strands one of which, the pair adjacent to 

 the forming nerve, produces the muscles of the future animal; while the remaining 

 pair are the beginnings of the genital glands. 



If now it should turn out that both epicardia of Herdmania contribute to each 

 bud, the dorsal tube (dorsal at the pericardium, Figure 11) giving rise to the branchial 

 sac at least, and the ventral one to the pericardium and heart at least, we should 

 have the homologues in the Herdmania stolon of two of the most important cell-masses 

 of the Doliolum stolon. It would then be in order to search with great care in the 

 first bud generation of Herdmania for the homologues of the Doliolum genital and 

 neural strands; and the organ-continuity from parent to bud which several authors 

 have believed to take place in all blastogenic ascidians would be realized. 



So far as Herdmania is concerned this is a perfectly reasonable speculation. 

 There should be no great difficulty in determining whether or not it corresponds to 

 what actually happens in bud production. Up to the present time I have not been 

 successful in getting any light on the origin of the buds, but I hope to be able to give 

 the matter the attention it deserves before long. 



io. The Sexual Organs. — Both ovary and testis are situated behind the intes- 

 tinal loop in the postabdomen; the latter, however, is not marked off in any way, 

 superficially, from the abdomen. 



The ovary is a simple oval structure situated about as far behind the loop of 

 the intestine as the extremity of the loop is behind the stomach. It is of small size. 

 The ova leave it before reaching maturity, further growth and maturation taking 

 place in the oviduct. Two views of the same ovary are shown in Figure 2 (PL XVIII) 

 and Figure 18 (PL XIX). Figure 19 (PL XIX) shows a section from the posterior 

 end of an active ovary, and Figure 20 one from the middle portion of the same ovary. 

 A section from the anterior end of the organ shows essentially the same structure 

 as that represented in Figure 19. In other words, at each end of the active ovary 

 the germinal epithelium is in the form of a plain disk or pad with no suggestion of 

 bilaterality. In the middle of the organ (Fig. 20) this pad becomes thrust out into 

 a deep ditch, which, however, does not draw into it the entire pad; so that here the 

 germinal epithelium becomes arranged in the form of a letter T. A few short branches 



