NOTES AND MEMORANDA. 203 



the margin of the longitudinal fissure ; or, in other words^ on the 

 margin of the aperture of the Vestibule. 



The upper portion of the digestive tube^ undergoes a change ; 

 the dorsal wall of the rudimentary intratentacular space is carried 

 backward and forms a cul-de-sac, the future Vestibule. On 

 the ventral wall, close to the integument^ is situated an open- 

 ing which is the buccal orifice. 



The anus is not yet developed. The rectum, at this stage, has 

 the appearance of a recurved cul-de-sac, closely applied to the 

 dorsal wall of the Vestibule. The anal orifice subsequently makes 

 its appearance at the point of union between these two. 



Stage 8. (Esophagus, stomach, and rectum are now distin- 

 guishable. The tentacles appear as small risings on the margin 

 of the cup, and as the latter consists of ectoderm and endoderm 

 the tentacles also possess the two layers. The former constitutes 

 the inner wall, the latter the outer wall of the tentacle which at 

 a later stage is covered with cilia. The number of tentacles is 

 less in the bud than in the adult, and amounts to ten in the 

 present species. «» 



At this stage the formation of the muscles commences ; they 

 are developed from the inferior portion of the mesodermic layer, 

 the upper portion giving rise to the parenchyma. The reason of 

 this division is evident ; it is the lower portion of the bud, in 

 which the muscular fibres are produced, that becomes the 

 peduncle. Each fibre seems to be formed by a single cell. 



The peduncle or stem is formed by the extension of the lower 

 part of the bud in which the pedal gland is lodged, but it 

 is only in the latest stages of the development that it is diiferen- 

 tiated. 



The author has noticed an interesting peculiarity in the young 

 buds of this species. Their tentacles are furnished with a very 

 long, fixed bristle, placed on the external side and close to the 

 summit. It is not present in the adult, and is therefore a pro- 

 visional structure like the pedal gland. The author conjectures 

 that it is a tactile organ essential to the bud when seeking a 

 place of attachment, but useless afterwards. 



If we compare the developmental history which I have now 

 summarised with that which we have from Vogt we shall find 

 very serious discrepancies between them. According to Salensky 

 and Nitsche the primitive contents of the bud are distinctly cel- 

 lular ; Vogt represents them as consisting of masses of homo- 



^ The author may perhaps mislead by speaking as he constantly does 

 of the uppermost section of the cavity scooped out, as it were, in the 

 endodermic mass, as a portion of the digestive tube. At an early stage it 

 seems to be distinguishable from the rest of the cavity, and subsequently 

 becomes the vestibule, which is in no sense a part of the digestive system. 



