158 



whitman: [Vol. I. 



longs. . . . Le r61e physiologique de ces fils consiste, 

 comme il me semble, dans la fixation reciproque de jeunes in- 

 dividus, tournes ordinairement I'un vers I'autre par leurs faces 

 dorsales et fixes a la parol ventrale de la mere par leurs ventouses 

 anterieures. Get organe dorsal n'existe cependant pas long- 

 temps ; il disparait sans laisser de traces avant la separation des 

 jeunes individus de la parol du corps maternel." 



Nusbaum and Hoff'mann (No. 4, p. 45) have both fallen 

 into the same error of supposing that the larvae attach them- 

 selves to the ventral side of the parent by the oral sucker. 

 The young are further, according to Nusbaum, fixed to one 

 another by means of glutinous threads formed by the " dorsal 

 organ." 



While studying the embryology of C. marginata and com- 

 planata, I noticed that larvae hatched from eggs that were taken 

 away from the parent and kept in a watch-glass, soon became 

 attached to one another in pairs. The point of attachment, how- 

 ever, was not dorsal, but ventral, just behind the part destined to 

 form the oral sucker. The attachment, as I have since learned, 

 is efi"ected through an adhesive secretion of the larval glands 

 above described. When the leech is allowed to remain over 

 the eggs until they hatch, the larvae become fixed to its under- 

 side, not by the still undeveloped oral sucker, but by the 

 secretion of the post-oral, ventral glands. I have never noticed 

 the " reciprocal attachment " by means of a " dorsal organ ; " but, 

 without further examination, I would not venture to dispute 

 Nusbaum's. statement. But the description and figures given 

 certainly awaken the suspicion that the "dorsal organ" is a 

 pathological formation. The larval glands which I have de- 

 scribed serve only the temporary purpose of fixing the young 

 to the parent leech at a time when neither sucker is sufficiently 

 developed to perform this office. As soon as the posterior 

 sucker becomes serviceable, it is used as an organ of attach- 

 ment, and the larval glands disappear ; at least, I have not been 

 able to connect them with any organ in the adult leech. 



The larval organs of adhesion occupy a position which cor- 

 responds to that of the Ganoid suctorial disc. The means 

 of fixation in the young fish (Amia), at least in the youngest 

 larvae, is an adhesive secretion. My attention was first called to 

 the secretion in Amia by Dr. Patten. 



