September 14, 1900.] 



SCIENCE. 



401 



THE DEVELOPMENT OF THE CONGEE EEL* 



On July 31st, Dr. Porter E. Sargent, 

 while on the U. S. Fish Commission vessel 

 Grampus on the tile-fish banks (about 40 

 miles south of South Shoal), secured a 

 number of species of pelagic fish eggs. One 

 of these is very probably that of the Conger 

 eel. 



I have followed the development of this 

 egg, and the larvfe hatched from it during 

 two weeks. In view of the fact that no 

 ripe eel eggs had been seen except in a lim- 

 ited region of the Mediterranean, a brief 

 resume of the results of my work on these 

 eggs may be of interest. But first a note 

 on the modern phase of the eel question 

 will not be out of place. 



In 1888, Eaffaele figured and described 

 a number of species of pelagic eggs which, 

 on account of the shape of the larvae they 

 produced, he referred to various species of 

 eels without a further attempt to refer 

 them to definite species. 



In 1897, Grassi published his series of 

 epoch-making works on the eel question. 

 He also found the eggs described byEaifaele, 

 but of more importance was his identifica- 

 tion of various species of Leptocephali as 

 the normal larval stages of various eels. 

 His conclusions in bi'ief were : 1st, that the 

 eggs of eels mature at great depths, 500 

 meters ; 2d, that the eggs, except occasion- 

 ally, develop at great depths ; 3d, that the 

 eggs give rise to a prse-larva, that this gives 

 rise to a larva (the Leptocephalus) , that 

 this in turn gives rise to a hemilarva which 

 finally is metamorphosed into the definitive 

 adult which may be much shorter than the 

 Leptocephalus from which it arose ; 4th, 

 that the egg of the common eel is without 

 an oil globule. 



The eggs secured during this summer are 



* By permission of Dr. H. C. Bumpus, director o£ 

 the Woods Holl Laboratory of the U. S. Fish Com- 

 mission. The details will be published by the Fish 

 Commission. 



very nearly, if not quite like one of those 

 described by Raffaele. They have all the 

 characters of a pelagic egg, and Grassi was 

 probably mistaken when he stated that 

 these eggs come to the surface only occa- 

 sionally. They are large, measuring from 

 2.4 to 2.75 mm. from membrane to mem- 

 brane. The yolk is in segments, and meas- 

 ures 1.75 to 2 mm. in diameter, thus leav- 

 ing a large perivitelline space. There are 

 usually several oil globules, one of which 

 is very much larger tlian the others. Some 

 of these eggs hatched on the fourth day, 

 others not until several days later. There 

 are several distinct and unique features in 

 the development, most of which have been 

 well described and figured by Eafiaele. (I 

 have not seen Grassi's illustrated work.) 



First among the peculiar features is the 

 shape of the yolk. This in later stages of 

 development becomes a long, slender mass 

 reaching from the heart along the base of 

 the alimentary canal to near the anus. 

 This mass becomes constricted in places 

 and the last seen of the yolk is a series of 

 small disconnected bead-like masses dis- 

 tributed at intervals along the base of the 

 alimentary canal. The j^olk mass in the 

 yolk sack diminishes very rapidlj', partly 

 by absorption, and partly, no doubt, by 

 becoming located in the sub-alimentary 

 yolk mass. A constriction is formed be- 

 tween it and the posterior yolk to which it 

 forms a sort of handle. The oil spheres 

 remain in the handle of the yolk mass. 

 This elongation of the yolk is a definite 

 adaptation to the elongate body and eeling 

 progression of the larva. 



The number of abdominal protovertebrte 

 is exceptionally large, numbering between 

 65 and 71 in the present case. 



The medulla becomes early and remains 

 late a large, conspicuous, thin-roofed ves- 

 icle. 



The color appears late. Only black pig- 

 ments appear. In the last stages reached it 



