402 THE AMERICAN NATURALIST. [VoL. XXXIV. 
quent development, it may be inferred that their occurrence in 
a state of nature is not inthe least improbable. Similar abnor- 
malities have been reported among other genera of hydroids, 
eg., Bunting (94) figures embryos of very similar character. 
Now whether all such anomalous planulz develop into normal 
polyp may not be easily determined. That many should not 
is only what constantly happens with the most typical. That 
some of them develop there is not the slightest doubt. In 
Fig. 6 is shown a specimen which had become fixed in the 
ordinary way and had developed tentacles upon apparently 
two polyps heads. And in this connection it may be noted 
that in many cases these anomalous processes have been seen 
to be resorbed into the body of the larva as it approaches the 
period of transformation. This may suggest that they are per- 
haps only temporary processes which may serve some tempo- 
rary function of doubtful significance. The larva shown in 
Fig. 4 might suggest that it had its origin as a twin from a 
single egg which had segmented somewhat as represented in 
Pl. III, Fig. 4, where development of the two halves of the 
ovum had gone on so apparently independently. But in no 
specific case, several of which had been isolated and watched 
with care, had any such form resulted. Nor, further, in speci- 
mens of similar larve carefully sectioned was there any special 
evidence of such an origin. 
I am rather disposed to consider them as due in all cases to 
the intrinsic prepotency of hydroids to bud and branch; for, 
as I have repeatedly observed, and as Pl. I, Fig. 8, will show, 
the budding propensity asserts itself very early in the polyp 
life. - 
Concerning abnormalities among adult hydroids of this genus 
I have made no extended observations. Bunting (94) refers to 
several cases among Hydractinia and Podocoryne. But in these 
the polymorphic conditions would, it seems to me, render them 
specially favorable subjects in which to expect such diver- 
gencies, while in Pennaria, at least, this element is lacking. 
In Fig. 1 of the text is shown a somewhat unusual, though 
possibly not abnormal, young polyp. As will be noted, its 
unusual feature consists chiefly in the total annulation of the 
