August 31, 1900.] 



SCIENCE. 



341 



a mistaken view, for the vesicles remain 

 after the eggs have been discharged, and 

 are quite as prominent in preserved speci- 

 mens as in those alive and bearing eggs. 

 As to variation in tentacles there seems to 

 have been little. These organs are so rud- 

 imentary that detection of variations in 

 them would be extremely difficult. 



Upon the whole this species seems to be 

 fairly constant in general structural fea- 

 tures and only in the deeper and micro- 

 scopic aspects are signs of degenerative vari- 

 ation specially apparent. The variation in 

 physiological habits to which reference has 

 been made are, however, very marked and 

 of quite as much significance as are those 

 more conspicuous morphological features 

 usually cited. I would offer this suggestion 

 that in those cases in which the medusae 

 perish early after discharging the ova, and 

 specially those which do not become free 

 at all, there may be some correlation be- 

 tween the atrophy of the chymiferous 

 canals and this shortlived condition. 



It is among the species of Gonionemus 

 that I have discovered the most notable 

 and numerous variations. Of these more 

 than five hundred specimens were exam- 

 ined, all of which were taken at "Woods 

 Holl during the summers of 1897-99. At- 

 tention was directed chiefly to a study of the 

 gonads, radial canals and tentacles. Of the 

 specimens examined only fifteen showed ab- 

 normal or unusual genital features. In five 

 specimens the gonads were atrophied upon 

 one of the radial canals and equally devel- 

 oped upon the others. One specimen showed 

 the gonads developed only upon one of the 

 canals. Six specimens showed no trace 

 whatever of gonads though they were of 

 full size and normal in every other respect. 

 Another specimen showed only traces of 

 gonads as two small knobs near the bases 

 of two approximate canals. 



There was considerable variation in both 

 the number and arrangement of tentacles. 



In reference to variation with age it was 

 found that on the smallest specimen ex- 

 amined measuring two mm. in diameter the 

 tentacles were twenty-nine, while on the 

 largest 19 mm. in diameter there were 68 

 tentacles. The number, however, was not 

 always proportional to the size. For ex- 

 ample, one specimen of 4 mm. diameter had 

 39 tentacles, while another of 6 mm. had 

 but 30 ; the largest referred to above had 

 68, while a specimen but 14 mm. in di- 

 ameter had 71, and two others of 15 and 16 

 mm. had 72 each. In only 11 of the 500 

 specimens were the number of tentacles be- 

 tween each radical canal equal and sym- 

 metrical. In the order of appearance of 

 new tentacles there did not seem to be any 

 definite regularity. For example the fol- 

 lowing from many observations may reveal 

 this more clearly : 



(1) 2-1, 2-1, 2-1, etc. (2) 7-1, 3-1, 

 7-1, 3-1, etc. (3) 11-1, 11-1, 11-1, etc. 

 In each case the 1 indicating the new 

 tentacle. 



In only a single specimen was there 

 found any bifurcation of the tentacles which 

 was so conspicuous a feature in Eucope. 

 In this specimen there were two tentacles 

 arising from a single sensory bulb and two 

 others showed bifurcation, one near the tip, 

 the other near the base. 



In the number and character of the rad- 

 ial canals there was the most marked exhi- 

 bition of variation. In number the varia- 

 tion was from two to six. Of the minimal 

 number, two, only a single specimen was 

 found, but it was in every way normal 

 other than this, and the correlated fact 

 that there were but two gonads. These 

 canals were continuous and divided the 

 body into halves. 



Of specimens with six canals several 

 were found, some of which clearly showed 

 the canals converging symmetrically to the 

 gastric pouch, but in a few cases the extra 

 two canals were found to result from an 



