1026 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [46] 



and ossifies directly. The anterior dorsal spines of Gasterosteus do not 

 seem to be preceded by a median fold, the latter havins^ atrophied be- 

 fore the papillae which develop into the dorsal spines have begun to 

 grow out. In Cyclopterus also no median fin-fold seems to precede the 

 anterior dorsal 5 a thick, low, hump-like outgrowth in front of the dorsal 

 fin-fold, leading to the development of the anterior dorsal directly. 

 Embryonic rays may jjossibly precede the formation of the permanent 

 rays of the first dorsal in Cyclopterus, judging from Agassiz's figures. 



It will thus be seen that the modes of development of the anterior 

 dorsal spines of Lophius and Gasterosteus, and the vexilla of Fierasfer 

 are similar, and that such a specialized mode of ray-development tends 

 to bring about the suppression of the fore part of the more archaic, dor- 

 sal median fin-fold ; that it also tends to lead to the suppression of the 

 embryonic fin-rays, which in all probability take no share in the for- 

 mation of the anterior spines in such forms, but retaiu such a relation 

 to the permanent raysouly in the i)osterior dorsal, anal, aud caudal, and 

 the soft rays of the pectoral and pelvic fins. 



The rays of the pelvic fin of Lophius are in like manner evidently not 

 derived from embryonic rays, but seem to be formed like those of the 

 anterior dorsal. 



These extreme forms of specialization lead us to anticipate other 

 equally singular modes of ray-development, which will probably only 

 differ in detail, because wo find after all that the principle upon which 

 both kinds of rays develop, namely, the separate form aud those con- 

 joined by a membranous investment, is essentially the same. The first 

 are formed in distinct epiblastic ])ockots of the skin, the latter in con- 

 tinuous or confluent ones, or in what I have throughout this jjaper 

 called folds. 



I have already referred to the peculiar way in which the rudin^ent of 

 the pelvic fin is pushed forward in Lophius, but 1 -nust also call attention 

 to the fact that an actual pushing forwards of the anterior dorsal also 

 takes place in this form, as a result of which the first dorsal ray is finally 

 brought to rest upon the frontal bones of the skull in the adult. In 

 3falthe, according to Gill, who has called my attention to the fact, the 

 anterior dorsal is shoved still further forward than in Ijophius, this 

 peculiarity being recognized as a family character by Gill in these words : 

 "Anterior dorsal ray in a cavity overhung by the anterior margin of 

 the forehead." In Fig. 1, PI, XI, the rudiment of the first dorsal ray 

 of the embryo of Lophius apj)ears above the anterior end of the me- 

 dulla spinalis and behind the medulla oblongata, but in some way it 

 is slowly advanced until, in Fig. 5, its base is above the mid-brain. A 

 new dorsal ray, according to Agassiz, next appears more anterior 

 to the one first formed, which may explain in another way how the ad- 

 vance forward of the most anterior rays of the dorsal is accomplished 

 by their development as later, single, and more anterior outgrowths. 

 There is, nevertheless, positive evidence that the originally formed 



