476 



PARENTAL CAEE AMONG FRESH-WATER FISHES. 



Fig. r}6. — Ad- 

 vanced Aspredo 

 egg with pedi- 

 fle of attacl^- 



men t ( ■; 4 ) . 

 After Wyman. 



could be made on the earlier conditions of the egg and the formation of its 

 pedicle. The pedicle is a flexible outgrowth from the common integuuients, 

 is about two lines in length, is attached to the skin by a slightly expanded 

 base, and spreads out at its summit into a shallow cup or " cupule." for the 

 support of the egg. It is composed almost entirely of fibrous tissue, invested 

 with a layer of tesselated epithelium. In some instances when the eggs were 

 but little advanced, numerous fusiform cells were detected among the fibers. 

 It is vascular, two or three vessels I'eaching to the cup, where they ramify 

 and form a somewhat extended capillary plexus [flgs. 50 and 57]. 

 The eggs vary according to the degree of development from 

 0.09 to 0.15 of an inch in diameter, and are covered with an 

 external homogeneous membrane, containing minute puncti- 

 form depressions — within this is a second, of a brownish color 

 and composed of epithelium. The embryos which were the 

 most advanced and just ready to hatch, had not as yet com- 

 pletely absorbed the yolk, and were coiled up within the mem- 

 liranes, which in consequence of the irregularities of the mass 

 formed by the embryo had no longer a spherical form. 



The eggs are retained in connection with the cup apparently 

 by adhesion alone, for as soon as the foetus escapes, the egg 

 membranes become very easily detached from the pedicle, and 

 this last as shown by some of the specimens undergoes 

 absorption. 



The relation of the embryo to the parent in this singular mode of gestation 

 can not be determined very accurately, but the vascular plexus in the cup 

 seems to be more than is necessary for the mei*e nutrition of the part. The egg 

 increases in size during incubation, those ova in which development had but 

 slightly advanced measuring from 0.09 to 0.11 of an inch in 

 diameter, while those nearly mature measured from 0.14 to 

 0.15 of an inch. How this increase of size of the embryo over 

 the original size of the egg is actually obtained I have no facts 

 to show, but either of two suppositions is probable ; it may 

 be by absorption of materials from the w'ater which surrounds 

 it, or from the capillary plexus of the pedicles, and in this case 

 in a manner analogous to that of Pipa. 



Even now nothing is known of the mating or court- 

 ship of the fishes. "Various attempts have been made 

 to explain, however; the latest and most probable ex- 

 planation was published by Vaillant in 1808. The eggs, 

 after being laid and fecundated, have a glutinous in- 

 vestment, and when the breast is pressed over them fig. 57.— ,ispr«/o 

 they adhere to it. It is the layer of the eggs — the female capillary pioxus 

 that presses the breast over the eggs. Irritation of the (x^)- After wy- 

 skin is set up then, and at the point of adhesion a 

 prominence arises, which becomes a sort of peduncle expanding into 

 a cupule embracing the proximal surface of the Qgg. It reminds one 

 of a mushroom with its stalk and head. In due time the eggs are 

 hatched and the shells or envelopes of the eggs may be left attached 

 to the mushroom-like expansion, or "oophore," as it has been named. 

 Finally these casts fall off also, the expansions become button or bead 



