i i ; 



absorbed. I have never seen in any fish embryos of the same 

 age, an instance where scales were developed or where the fins 

 had approximated their adult condition so nearly as in this case. 

 The only instance known to me at this writing where a continu- 

 ous dorsal and ventral median fin-fold is never developed, is in the 

 case of Syngnathus, where the caudal rays are developed before 

 the dorsal ones. Whether the unpaired fins of Gambusia are 

 or are not derived from such a fold would be an interesting obser- 

 vation. A marked acceleration is also noticeable in the develop- 

 ment of the brain, a study of which, by means of sections, as 

 compared with that of the adult, has furnished me with some 

 valuable clues in following up the development of Teleostean 

 brains in general. 



To sum up, this fish begins an independent career as far devel- 

 oped as when the shad, cod, mackerel, bonito and many other 

 fishes are from three to six weeks old. By so much it has the 

 advantage over those types in the struggle for existence in that 

 it is ready to feed, to pursue its prey discriminately, as soon as 

 it is born, while the other forms alluded to are comparatively 

 helpless until some time after they have absorbed their yelk sacs, 

 although most of them by that time have acquired mandibular, 

 maxillary or pharyngeal teeth or both. The Fish Commission 

 authorities need never be uneasy about the fate of the top-min- 

 nows ; they will take care of themselves ; their species is sure of 

 survival. But our study, it would seem to the writer, has not 

 been in vain, because, even though the fish is too small to be of 

 any practical value, it has taught us that where nature has so 

 effectually provided for the protection of the young fish, she does 

 not require one adult to produce as many embryos. In Gam- 

 busia twenty-five to thirty young is perhaps the limit of produc- 

 tion for a single female ; in Apeltes, or the four-spined stickle- 

 back, the male of which is provided, according to my observa- 

 tions, with a spinning apparatus with which he fabricates a nest in 

 which the young are hatched and taken care of, the number of 

 eggs is from fifteen to twenty. Contrasting these small numbers 

 with 100,000 to 3,000,000, the number of ova easily matured in a 

 single season by a single female of many anadromous and marine 

 species which have heavy, adhesive or floating eggs, it would 

 appear that the quantity of germs produced by different species 

 of fishes is in some way proportioned to their chances of survi- 



