226 



HARGITT. 



[VOL. II. 



While in most cases these observations were made upon speci- 

 mens under artificial conditions, namely, aquaria of variable 

 sizes, etc., still the variations occurring were exhibited by 

 larvae under identical conditions, such as they were. 



Under the head of abnormalities in immediate connection 

 with these observations, attention was also directed to certain 

 variations in the morphology of the larvae and early polyps. 

 Among these may be mentioned 



1. Twin-planulae, - - planulae with bifurcated ends, irregular 

 bud-like outgrowths, etc. (Cf. op. cit., Figs. 4-6, and 8, PL i.) 

 It was suggested that they were probably due " to the intrin- 

 sic prepotency of hydroids to bud and branch." While this 

 is probably an explanation of the facts, that they exhibit 

 interesting variations from the ordinary is not discredited on 

 that account. 



2. Attention was also directed to an interesting polyp form 

 (op. cit., Fig. i of text), which presented so marked a varia- 

 tion as to give rise to some doubt concerning its Pennarian 

 affinities. In view of the rather large range of variability 

 exhibited by the medusoid and larval persons already consid- 

 ered, I am still convinced that this is only a further illustration 

 of the same principle. Indeed, I have during the present sum- 

 mer observed in other polyps reared under similar conditions 

 the same variation from total annulations to less and less 

 degrees. A few additional annulations of the hydroid perisarc 

 is matter of no special surprise. A complete annulation of 

 the early and plastic colony, while quite unusual, need not be 



regarded as improbable or especially strange. 

 Another feature which may perhaps rather 

 be designated as a monstrosity, or incidental 

 excrescence, may be noted in this connection ; 

 namely, certain wartlike or pustular vesicles 

 which often appear at various points on the 

 exumbrella of the medusae. These are fairly 

 represented in Fig. i. The figure indicates 

 relative positions where they are most likely to occur, though 

 in no case have I noted more than one upon a given specimen. 

 ... A similar structure is referred to by Agassiz ('65) and 



IMC;. T. 



