556 Chas. W. Hargitt. 



As suggested above, it seems reasonably clear that the excess of 

 rhopaha may be accounted for in the manner already proposed. 

 But it remains to consider those cases in which the number of 

 marginal lobes is in excess of the number of rhopalia. Of these 

 there were found seventeen cases, as against twenty-three of the 

 former. It is quite obvious that for these a different explanation 

 must be found. We are here limited to two alternatives, namely, 

 either there are cases in which for some reason there has been a 

 failure of a given lobe to develop its usual organ; or on the other 

 hand there may possibly be a subsequent and independent origin 

 of an extra lobe. While I have found undoubted cases of the 

 occurrence of the former condition, and am constrained to regard 

 it as the more usual and probable explanation, at the same time 

 I have found an occasional case in which a belated lobe appears to 

 arise after the ephyra has become free from the strobila, but at 

 the same time it must be admitted that in these cases there is 

 usually found the accompanying rhopalium, though this is not 

 always true. I am therefore constrained to consider both alter- 

 natives as possible, though giving to the first the larger 

 probability. 



A few unusual features in the marginal and rhopalial variations 

 call for a merely passing notice. Fig. i, showing an ordinary twin 

 rhopalium, calls for little note aside from the statement of fact that 

 it plainly occupies the position and relation of a typical organ, 

 namely, the terminus of a single canal. And in this connection 

 it may be well to recall that in the early ephyra-life all the canals 

 are simple, that is, unbranched. It is only during the progress of 

 metamorphosis that the complexity of the adult canal system is 

 gradually differentiated. 



Figs. 2, 3, show a series of extremely interesting variations of 

 graduated complexity. The first shows a trifid condition of the 

 otherwise normal ephyra lobe, though with the added abnormality 

 of twin rhopalia in one of the notches. In the second there is 

 shown a quadrifid lobe, the lappets of the median pair being small 

 and not particularly remarkable, while in each notch of the outer 

 lappets is a normal sensory body. Several other figures show 

 similar features. 



Among 486 ephyrae taken in the "eel pond," Woods Hole, in 

 April, IQ02, the variants numbered 144, or 29.6 per cent. 



