NOTES AND MEMORANDA. 301 



at first quite closed, but afterwards opens on the exterior by a blasto- 

 pore, produced by the separation of those endodermal cells which 

 occupy the position of the four cells originally iuvaginated, on the 

 ventral surface of the embryo. At a still later stage the blastopore 

 thus formed closes up, both mouth and anus being subsequently 

 formed as invaginations of the ectoderm. 



The chief fact about Lepralia is the confirmation of the author's 

 previously expressed opinion that the structure called " stomach " by 

 Barrels is really a sucker. 



The two Bowerbankia-lsLTVse were pear-shaped, with a mantle 

 covering the dorsal and ventral surfaces, and a mantle-cavity opening 

 by an aperture at the small end of the embryo. The larger specimen 

 had on its flattened ventral side an elongated ciliated aperture, in 

 relation with which, in the interior of the body, was a granular mass 

 representing the endoderm. On the ventral side of both was a longi- 

 tudinal groove, bounded by two folds, and resembling the medullary 

 groove of a Vertebrate. In the smaller specimen this was continuous 

 along the whole ventral side ; in the larger it was interrupted by the 

 ciKated aperture just mentioned. 



In both larvaj there was a shallow annular constriction round the 

 middle of the body, and, at the same place, a thickening of the mantle. 

 A second constriction, with a corresponding thickening of the mantle, 

 occurred between the first, and the thin end of the body. Corre- 

 sponding to these constrictions, there was, in the smaller larva, a 

 weak indication of segmentation of the ventral (supposed medullary) 

 folds. 



The early stages of develop:nent in the Ctenostomata (the group 

 to which Bowerbaukia belongs) resemble in a general way those of 

 Tendra, but the gastrula approaches more nearly to the simple archi- 

 gastrula. 



In a further communication Repiachoff * has studied more care- 

 fully the later developmental stages of Tendra, of which only a brief 

 account was given in his former paper. He states that he has proved 

 the sucker of the embryo (" stomach," Barrois) to originate as a 

 thickening of the ectoderm on the ventral side of the body. He also 

 describes the blind endodermal sac or midgut of the embryo as 

 extending uninterruptedly quite to the upper end of the body ; above, 

 therefore, the involution which becomes the foregut. Subsequently 

 this ujiper portion of the endoderm becomes scjjarated from the 

 remainder, and forms a mere accumulation of cells in close proximity 

 to the oral furrow. The remainder of the endodermal sac fuses with 

 the foregut involution, and forms with it a semi-lunar alimentary 

 canal. 



Presence of a Segmental Organ in the Endoproct Polyzoa. — In 



October, 1877, Hatschek of Prague discovered in Pedicellina ecldnata, 

 both in the larval and adult state, a vibratile canal which he 

 apparently could not quite make out, and which he compared to the 

 vibratile organs of the Eotatoria. M. L. Joliet has confirmed t 



* ' Zool. Anzeigcr,' ii. (1879) 68. 



t 'Cuniptes Pieudus,' Ixxsviii. (1879). 



