Notes on Meduse of the Western Atlantic. 145 
{ocate. I had not entertained any idea of finding a large and conspicuous 
hydroid, but the minute proportions of the creature when finally discovered 
surprised me. The polyp, growing singly, was so exceedingly delicate that 
it was almost invisible to the unaided eye. Only one specimen of the entire 
number that came to light, over a dozen in all, was large enough to be at 
all readily seen without a lens. This, though slender and transparent, meas- 
ured 1.5 mm. in height. It is no wonder, then, that this form has not been 
a familiar sight to visitors in these waters! 
During the time that the search was being carried on in the moat, careful 
watch was being kept over the medusz which were brought into the labora- 
tory every day. Only one individual was found in which the gonads showed 
any sign of activity. In this, a single spherical mass appeared upon the 
manubrium, above the gastric enlargements. This medusa was kept under 
frequent observation for some days, but the only perceptible change was 
an increase in the size of the egg, if such it was. The specimen disappeared, 
finally, without throwing any light upon the laying or development of the egg. 
Filiform tentacles——The absence of tactile hairs from the tips of the 
lower row of tentacles has been mentioned. The function of these pro- 
cesses, or “ false tentacles,” as Hincks! terms them, is problematical. It does 
not seem to be at all certain that they are intended to perform the function of 
tactile organs, inasmuch as their sensitiveness does not exceed that of the 
adjacent parts. Hincks says: “ Their function seems to be to give notice of 
the presence of animalcules or other prey. If anything touches them, the 
head and upper arms are instantly bent towards it.” I tried to find out 
whether this same reaction occurred in our species, and found that it did. 
But it did not make any difference whether the stimulus was applied to 
the tip end of the process, or to some other part of it, or to the column of 
the polyp nearby. It is likely that in the other species the tactile sense is 
more localized. 
Feeding reactions—The same eagerness in the presence of food which 
was noted in the medusa also characterizes the hydroid. The column of the 
polyp stands up stiffly and without any sign of life when there is no prey 
near. The capitate tentacles around the mouth droop a little at the tips, 
and the filiform tentacles below are straight and stiff. But let the smallest 
speck of an animalcule come along and touch the polyp, and it suddenly 
becomes flexibility itself. The column bends and twists, the oral tentacles 
reach after the prey, and even the slender tentacles below manifest signs of 
life. Plate 2, figure 7, is a drawing made to show the attitude of one of 
the polyps at the instant that a small worm, which had become partially 
fixed to the column by the nematocysts, made good its escape. 
Reproduction.—I was unable to see that any definite gonophores were de- 
* Hincks, loc. cit., p. 64. 
