Notes on Medusa of the Western Atlantic. 139 



storms, of plant and animal life which encourages the growth and develop- 

 ment of other species. 



An interesting opportunity is offered by our species to see whether the 

 concretions in the tentacles, increasing the weight of the organism, and the 

 strong suctorial processes on the tentacles as many as 25 to 30 in each 

 individual will disappear or become reduced as a result of their withdrawal 

 from the rough weather they seem intended to combat. Observations ex- 

 tending over a series of years would be of value in determining this point. 

 And yet, while apparently no longer a necessity as a protection against the 

 elements, it is by no means certain that these peculiar modifications are not 

 useful to the jelly-fish for other reasons. It seems not at all improbable, 

 indeed, that the daily and normal activities of the medusa are to some extent 

 dependent upon the heavy tentacles and bell-margin, and that the prehensile 

 organs upon the tentacles are of much use in the feeding habits. The suc- 

 torial processes are very strong, much stronger than would seem at all neces- 

 sary for the carrying out of the routine suggested, and evidently capable 

 of far greater resisting power than that which is brought into requisition in 

 the quiet life of the animal. How long is it likely that these organs will 

 retain their strength or be kept in their present numbers, when there is no 

 longer any tax upon their strength ? It seems improbable that they will keep 

 their present efficiency for long in the absence of such requirements. 



Distribution of the genus. The remarks in the last paragraph upon the 

 possibility of degeneration of the suctorial powers of Cladonema mayeri 

 apply with particular force to any representative of this genus. This is the 

 case because of the evident tendency to variation amongst its members. 

 Every writer upon the group calls attention to the large percentage of indi- 

 viduals having some other numerical arrangement of tentacles, radial 

 canals, and parts of manubrium, than the typical one. In the species 

 under consideration the irregularity did not seem to be so great as in the 

 others which I have seen. Several counts showed a varying number of parts 

 in about 20 per cent of the individuals. Instead of 9, there are present 8, 

 ro, or ii ultimate branches of the radial canals, and a like number of ten- 

 tacles are present, or, in cases of normal numbers of tentacles and canals, 

 the 6-parted manubrium may be varied into one possessing 5 or 7 parts. No 

 single type of variation exceeded 8 per cent. 



In view of this tendency to vary, it has been thought by some that it was 

 a mistake to give specific or even lower rank to the different types. They 

 should rather be regarded as nothing more distinct than varieties. I ad- 

 mit that it is possible that transitional types are in existence. It would be 

 rather troublesome to apply breeding tests to the different types, and estab- 

 lish their identity or separateness by their sexual affinity or antagonism. 

 The only course that is left open to us seems to be to decide whether the 

 percentage of varying individuals out of any very large number is sufficient to 



