. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 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, irreg
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 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 ; 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 represente
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