178 H. H. NEWMAN. 



ORIGIN, DEVELOPMENT AND DISAPPEARANCE. 



In order to determine how early in the season the contact 

 organs begin to make their appearance, a number of specimens 

 of the two species most accessible, F. heteroclitus and F. majalis, 

 were very kindly collected for me by Mr. G. M. Gray, of the 

 Woods Hole supply department. The results of the examina- 

 tion of these specimens are shown in the following tables : 



TABLE I. 



(F. heteroclitus males, collected April 27, 1907.) 

 No. of Specimens. Distribution of Contact Organs. 



5 A few on the posterior lobe of the anal tin. 



3 Fairly numerous on the tips of nearly all of the rays of the 



anal fin. 



I Plentiful on the rays of the posterior lobe of the anal fin. 



I Scattering distribution over nearly the whole area of the 



anal fin. 

 I Numerous on all of the rays of the posterior two thirds of the 



anal fin. 

 8 None. 



According to these data the earliest appearance of contact organs 

 in this species is on the anal fin, especially on the posterior lobe 

 of the latter. They appear first upon the distal ends of the rays 

 and from there extend gradually toward the base. One is tempted 

 to suggest a correlation between the early appearance and the 

 functional importance of these organs. There seems to be no 

 doubt that the anal fin is of prime importance in clasping. 



TABLE II. 



(F. heteroclitus males, collected May 14, 1907.) 

 No. of Specimens. Distribution of Contact Organs. 



3 On anal fin only. 



z On anal fins and on the scales of the body zone between the 



dorsal and anal fins. 

 5 None. 



Specimens taken in large numbers about two weeks later nearly 

 all showed the full equipment of contact organs. The develop- 

 ment, therefore, is a very rapid one, taking place largely within 

 a fortnight. 



The conditions in the other species (F. majalis) were some- 

 what different. Specimens collected April 27, 1907, showed no 

 contact organs. Those collected on May 14 of the same year 

 showed conditions tabulated as follows : 



