13S MUKiENID^. 



tween Hyoprorus and Nettastoma is striking. It is true that the 

 form of tho abdominal organs is very different ; but these organs un- 

 dergo the greatest changes from the hirval period to the perfect stage 

 in all animals subject to a metamorphosis. 



Assuming, then, that the Leptocephalides are undeveloped crea- 

 tures, and especially that L. morrisii is a young Conger, the question 

 arises whetlier they represent a normal stage in the developmental 

 series of Congers, or whether they are individuals arrested in their 

 development at a very early period of their life, yet contimdng to grow 

 to a certain size without corresponding development of their internal 

 organs, and perishing ivithout having attained the cJiaracters of the 

 perfect animal. I do not think that anything but actual observation 

 of the living animals vrill settle this question ; from an examination 

 of specimens preserved in spirits, I can direct attention to the fol- 

 lowing points only : — 



1. Young, perfectly developed Congers are not common in collec- 

 tions. The smallest example I have examined is 4^ inches long — that 

 is, smaller than numerous examples of L. morrisii. Therefore, if the 

 young Conger is normally subject to a metamorphosis, this change is 

 not accompanied by a corresponding growth of the entire animal, 

 and the similarity of size of the larva and perfected animal cannot 

 be brought foi-ward as a proof that no such evolution takes place. 



2. Specimens with a more cylindrical body, with the muscular 

 system more developed (Hclmichthys), are certainly merely a more 

 advanced stage of the true Leptocephali. The snout is a little more 

 elongate, much resembling that of an adult Conger ; yet there is no 

 perceptible progi'ess in the development of the vertebral column. 

 These examples are less common than the compressed forms. Their 

 occurrence does not help lis in deciding the question as put above. 

 They may be merely a stage of a normal metamorphosis, whilst, on 

 the other hand, it is qidte possible, and consistent with analogous cases 

 in other classes of animals, that, if the Leptocephali are abnormally 

 undeveloped forms, some individuals may in certain respects be more 

 developed than others. 



3. It is evident that there are distinct forms even among the 

 typical Lej^toeejihali. They are chiefly characterized and distinguished 

 by the form of the head and snout. This indicates a different origin ; 

 but I do not possess the means to refer these forms to their proge- 

 nitors. It is probable that Myrus, Ophichtlujs, perhaps also Murcena, 

 have their Leptocephaline forms. Eut whilst I admit this, I must 

 confirm Prof. Carus's observation, that, at least as far as the Medi- 

 terranean Leptocciihnli arc concerned, the variations in the situation 

 of the vent, in the dentition, in the form of the body, itc. are so 

 numerous and inconstant that no attempt should be made to dis- 

 tinguish and describe them specifically. This extraordinary varia- 

 bility favours the siqiposition that they are individiuils abnormally 

 arrested in their development. 



The Leptocephalides beiiig composed, as stated above, of very hete- 

 rogeneous elements,! can place with the Maranidie o\i\y Lepiocephalus 



