Development and Mode of Growth of Diplogeaptus. 233 



he called " Dawsoniae," in many instances attached, when small, to 

 the cellules of Gr. Sedgioicki ; sometimes to the apex of a 

 theca, while sometimes they appear to spring from the 

 common canal 'or from the under surface of a theca. The 

 author compalres them with the "gonophores" of the recent 

 Hydroids, on account of their external processes and their like- 

 ness in form, while they differ in having a corneous envelope. 

 He believed that they were attached to the sides of polypites or 

 to gonoblastidia, although he admits that they have not been cer- 

 tainly detected in direct communication with the poly pary of any 

 Graptolite. 



The gonangia described by Hopkinson in Ann. & Mag. of Kat. 

 Hist., 1871, vol. YII, p. 317, resemble closely the appendages 

 made known by Hall. Hopkinson states, on this occasion, that 

 the connection of IS'icholson's graptogonophors with the Grapto- 

 lite is not proved. 



Alimann, who had an opportunity of studying English speci- 

 mens closely resembling the American ones, denies their having 

 been capsular bodies. They appear to him rather to be hollow 

 laminaB ; but, on account of the regularity of their disposition, 

 he does not regard them as accidental growths. He thinks that 

 their connection with the gonosomal system is probable, and 

 compares them with the leaflets which compose the corbulae of 

 certain Plumularidoe^ where the gonangia" are developed in 

 groups, and each group is sustained in a common, basket-like 

 receptacle, which is a metamorphosed ramulus. He finds his 

 view supported by the fact that in each case where they have 

 been satisfactorily observed, the thecae became suppressed in 

 that part of the fossil which carries the appendages. 



I have not yet found any appendages similar to those discovered 

 by Hall. 



As to the "ovarian vesicles," which Nicholson found associated 

 with the Graptolites, Alimann thinks their connection with the 

 Graptolites to be purely accidental, on account of their origin 

 from the walls of the thecae. Indeed, the fact that Nichol- 

 son describes them as being attached to different parts of the 

 rhabdosome, makes it very probable that these vesicles came only 

 accidentally in contact with the rhabdo-ome. On. the other 

 hand, I would like to remark that Alimann himself described 

 30 



