EMBRYOLOGY OF THE STARFISH. 



CHAPTER FIRST. 



ARTIFICIAL FECUNDATION, AND HISTORY OF THE DEVELOPMENT OF THE LARVA 



Differences of the Sexes. — Since the existence of different sexual organs in separate 

 individuals was first pointed out among the lower animals, the tendency of every 

 additional advance in our knowledge of their structure has been to bring out more 

 fully the differences of sex between them. But recently, we did not even know that 

 among the Medusae there were male and female individuals ; and yet, at the present 

 day, it is a comparatively easy task to distinguish, among the larger Jelly-fishes, the 

 males from the females. The difference of coloring is very striking. The sper- 

 maries of the males are often brilliantly tinged, while the ovaries of the females are 

 of duller hues. We 1 thus find among Jelly-fishes the first indication of an almost 

 universal law in the animal kingdom, and which is nowhere carried out to so great 

 a degree as among Birds. A casual observer could not fail to distinguish a male from 

 a female Amelia, — though the great difference in the coloring of the males and 

 females had not been perceived by naturalists till it was first pointed out by Professor 

 Agassiz, in Aurelia flavidula Per. et Les. In Melicertum, in Turris, in Staurophora, in 

 Circe, a glance will suffice to determine the sex of the individual ; while a single look 

 through a magnifying-glass will reveal to us the sex of the smaller species, such as 

 Eucope, Pennaria, Euphysa, and the like. The difference of the sexes of some Echino- 

 derms is easily perceived by their difference of coloring at the time of spawning ; 

 among them are our common Starfishes and our Sea-urchins. 



The males and females of our common species of Starfishes, Asteracanthion pallidus 

 Aff. (A. vulgaris Stimp.?), and Asteracanthion berylinus Agass., can readily be distin- 

 guished by their difference in coloring : all those having a bluish tint being invariably 

 females; a reddish or reddish-brown color indicating a male. Among the many 



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