Some PecuUaiities of the Ova of Fishes. 8i 



ON SOME PECULIARITIES OF THE OVA OF FISHES. 

 By Dr. James A. Henshall. 



Read at the Society's Scientific Meeting, July 3, 1888. 



Fishes constitute the oldest as well as the most numerous forms 

 of vertebrate life, which might naturally be inferred when we 

 consider that nearly three-fourths of the surface of the globe is 

 covered with water, and that all of this "world of waters," from 

 the vast depths of the boundless sea to the tumbling rill of the 

 mountain side, is teeming with fish-life, from the huge vampire or 

 devil-fish, measuring twenty feet across its wing-like pectorals, to 

 the little naked, nest-building stickle-back ; or from the cruel, 

 rapacious scourge of the ocean, the man-eating shark, to the diminu- 

 tive, transparent darter of the spring brook, barely an inch in length. 



We might also infer from this great difference in the size, form 

 and habits of fishes the fact that there is more diversity in the eggs 

 of fishes than in any of the oviparous vertebrates. 



While most all of the sharks and rays are viviparous, all of the 

 true fishes, witli a very few exceptions (which bring forth their 

 young alive), are oviparous; and it is my intention to merely 

 allude to some of the peculiarities of the ova of a few of the mul- 

 titude of piscine species inhabiting the waters of the earth. 



Among birds, from the ostrich of the old world to the humming- 

 bird of the new, we find a close similarity m the form and con- 

 struction of their eggs. Likewise, in regard to the ova of reptiles, 

 we observe the same general likeness— those of the turtles all 

 resemble each other, as do those of the serpents. The ova of 

 batrachians approach m>>re nearly those of fishes in appearance, 

 but they still preserve a general and characteristic similarity. 



The ova of all of the true fishes are spherical in form, though in 

 some of the related or lower forms, they are oval or semi-ellipticaL 

 The ova of some species, as the salmon, brook trout, shad, etc.,, 

 are separate and apparently smooth on the surface, like so many 

 pellets of shot, while those of other species are provided with 

 minute threads or filaments, by means of which they become 

 attached to each other or to foreign substances. Some adhere 

 singly to weeds or other objects, some float singly, some sink to 



