1028 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. [48] 



sal in connection with the neural spines of the fourth to the seventeenth 

 vertebrae, and those of the anal with the hsemal spines of the tenth to 

 the seventeenth vertebrae. The vertebral column in Molacantlius ter- 

 minates abruptly with the seventeenth vertebra, and no caudal chain of 

 interspinous bones can be traced. The liver is small, when compared 

 with that of the young [Mola]^ and is composed principally of a large 

 right lobe overlying the stomach. The stomach is small and the intes- 

 tine is short, making but two turns like the letter S, while in [Mola\ it is 

 long and has five or six turns or coils. The arrangement of the mus- 

 cles and bones of the head is in general about the same as in [Molay 



These extracts from Mr. Putnam's article embody essentially all that 

 he has added to our knowledge of the morphology of the young stages 

 of Mola rotunda, as we will show all of them to be in accordance Avith 

 the views of Liitken, Steenstrup, and Giinther, but the position of 

 those authors will be here fortified by conclusions based on another 

 series of comparisons and on the general principles of development, 

 which may be depended upon to (jlear up many facts of very uncertain 

 significance when viewed merely in the light of the comparative anat- 

 omy of the adults. 



Mr. Putnam does not seem to have thought of the fact that the differ- 

 ences which he had indicated as existing between Molacanthus and Moki 

 juv. were just those differences which another investigator would seize 

 upon, guided by the light which embryological principles would afford 

 him, in order to show that Molacantlius was only a younger stage of Mola. 

 Nor does it seem to have occurred to any one to look and see if the gener- 

 ative organs of Molacanthus were developed to maturity, or whether they 

 were present only as genital folds or ridges of the peritoneum in the up- 

 per posterior part of the abdominal cavity, and therefore in an imma- 

 ture or larval condition. The reco_>:uition of ^lolacanthus as an adult 

 form, therefore, rests on pure assumption, and cannot be demonstrated 

 with the help of the anatomical data now at our command. 



On Mr. Putnam's investigations the embryologist may very evidently 

 base conclusions diametrically opposed to those entertained by that 

 author. For example, in Molacanthus the intestine is short, and has but 

 two bends, or is sigmoid in its coarse, while in the form thought to be 

 the young of 2[ola the intestine is long and has five or six turns or coils. 

 This is what should have been expected on embryological grounds, for 

 the intestine of young fishes is always straight at first, and only be- 

 comes bent so as to develop more coils or loops as the form approaches 

 maturity. The liver also develops unsymmetrically in many young 

 fishes, and to urge its relatively smaller size in Molacanthus, as com- 

 pared with Molajwv., where it is n^ore symmetrical and relatively larger, 

 is simply to ignore the light which einbiyology might have thrown upon 

 the matter, when all difiiculty on this j><)int would have immediately 

 disappeared. 



In the same way the differences observed in the atrangement and re- 



