95 



I have been vinable to obtain any confirmation of the account given by Masterman of 

 the changes in the position of the arms during the development of the bud. I have already 

 discussed this question (p. 36), and I will merely repeat in this place that I believe that the 

 complicated rotation of the arms described by that author does not occur, and that the hypothesis 

 suggested to explain it is accordingly unnecessary. 



In examining sections of buds of various ages, in C. dodecalophiis and C. gracilis^ I have 

 come to certain conclusions which do not agree with those of M.\sterman (cf. p. 91). There 

 can be no question that the structure described by him as the "subneural sinus", in the later 

 stages at least, is the pericardium. Masterman has more recendy (99, 2) admitted that the 

 space which he at first described, in the adult, as the subneural sinus is in reality a pericardium, 

 similar to that of Balanoglossus, although in his latest paper (03, p. 725) he states that it is 

 evident that in his account of the budding "the origin of the pericardial sac must have been 

 overlooked". From this I understand Masterman to mean that while he would admit that the 

 "subneural sinus" shewn in figs. 60 and 81 of his paper (98, 2) on the budding is the pericar- 

 dium, he would probably maintain that the "subneural sinus" shewn in earlier stages such as 

 figs. 36, },'] and 39 was really a vascular space. I am inclined to think, on the contrary, that 

 the "subneural sinus" shewn by Masterman in figs. 37 and 39 at least is the same structure 

 as that of the later stages (figs. 80, 8 1 ). In all these cases the organ is represented as having 

 no proper wall of its own, but as being a blastocoelic space between the ectoderm and the 

 coelomic epithelium. This does not agree with my own results, and in further criticism of 

 Masterman's fig. 39 I must point out that I have reason to believe, from my study of the 

 same species, that the proboscis-cavity is not really continuous with the paired body-cavities at 

 a stage so late as this, nor does the intestine pass freely through the body-cavity from its point 

 of origin in any of the young specimens which I have had under observation. 



The buds of C. dodecalopJms make their appearance, as pointed out by Masterman, on 

 either side of the middle line of the sucker-like base of the stalk, and on its anterior surface. 

 F'&- 7i of C. gracilis^ would at first sight seem to imply that the buds of this species are 

 developed on the posterior side of the sucker. It must, however, be remembered that in the 

 long-stalked species of Cephalodisats^ rotation of parts of the stalk round its own longitudinal 

 axis are commonly observed, as may be seen by an examination of the course of the longitudinal 

 muscles in entire preparations, or of the anterior nerve-tract in sections transverse td the long 

 axis of the stalk. There is evidence of twisting in the stalk of fig. 7, and I think that the bud 

 which faces posteriorly in the preserved specimen is really situated on the anterior side of the 

 sucker. It is certainly a lateral bud, and a still younger bud is indicated by deeper focussing 

 in the same specimen. 



In its earliest recognisable condition (PI. XIII, fig. 164, b)) the bud of C. dodecaloplms 

 is a spherical vesicle lying in the thickness of the parent ectoderm, and formed as an outwardly 

 directed bay of the basement-membrane. The interior of the parent-stalk is occupied by muscles 

 and connective tissue which are developed to such an extent that no definite coelomic space 

 remains, although the condition of the stalk throughout the development of the bud shews that 

 the whole of the tissue internal to the basement-membrane of the epidermis must be regarded 



