BULLETIN OF THE UNITED STATES FISH COMMISSION. 283 



EVEI-OPMEIVT OF TBBE SILVER GAU («EI.O:VE I^OIVGIROSTRIS), 

 WlTai «>i;SEB5VATIONS 0:V THE OEIVESm OF THE liTOOS) 1^ KITI- 

 RRV(» FINED ES, AIVt> A C'OMrAKISOIV OF FISH OVA WITH T«IOSE OF 



oo'iiEii vekti:brates. 



By JOIIIV A. RYD£R. 



The development of the fish we are about to describe is in itself of 

 little practical importance, but because it serves to illustrate in a very 

 remarkable way the manner in which the blood is originated in an embryo 

 teleosteau, it may serve to teach us a useful lesson as to the origin of 

 the elements of the blood in other forms, such as the salmon, whitefish, 

 &c., a complete knowledge of which it is desirable that we should pos- 

 sess, in order that we may more fully comprehend the evolution of their 

 structures in the egg'. Another matter of peculiar interest is the pres- 

 ence of numerous filaments which are distributed over the whole sur- 

 face of the very thick egg-membrane, and which are at first tightly 

 coiled around the latter, but which afterwards uncoil, when they twist 

 together into strands, and also become entangled with the filaments 

 arising from other eggs so as to bind large numbers together into large 

 clusters, is^ot only are large masses of one brood thus joined together, 

 but it is also found that if the recently spawned ova come into contact 

 with slender objects in the sea they immediately wind their filaments 

 about the latter, and are by this means suspended very securely, so 

 that with the ebb and flow of the tides they are constantly bathed by 

 difierent water. It appears that in this way their incubation would be 

 favored, for after their fixation by the filaments or threads, the ebb and 

 flux of the tide sweeping through and by the clusters of eggs would in 

 eflect very closely resemble the conditions to which fish ova are ex- 

 posed in ihe process of artificial incubation. It would seem that in this 

 case nature had anticipated the protectire designs of man in develop- 

 ing a means by which the survival of a species might be insured. How 

 the filaments have been evolved it appears impossible to the writer to 

 explain; he can think of no rational hypothesis of evolution by which 

 it would be possible to account for their development. AVhile the ova 

 of a comparatively useless fish are thus provided with a means of pro- 

 tection and suspension, not only to favor their incubation, but also to 

 keep them from being overwhelmed with the ooze and mud of the sea- 

 bottom, there are other species of considerable value, the eggs of which 

 are probably provided with similar thread-like appendages. I allude 

 to the so-called "jumping-mullet," Muyil albula, a fish much esteemed 

 lor the table in some places along our eastern coast. It therefore be- 

 comes a matter of some importance to know how many of our native 

 species have their ova provided with filaments for the purpose of at- 

 taching them to each other and to foreign objects. 



Professor Haeckel appears to have been the first to describe fish ova 



