1869.] CANADIAN ZOOLOGY. 421 



number. The coralluin or skeleton is of a corneous and fibrous 

 nature, and the animals are connected by numerous canals tra- 

 versing its substance. 



THE SEA JELLIES. 



One of the best representatives of this order on our coast is 

 the great blue Jelly-fish, Cyanea Arctica, (Fig. (i6), which is often 

 found in the Gulf of St. Lawrence and on the Atlantic coast of 

 Nova Scotia, a foot or more in diameter, and is said sometimes 

 to attain the enormous diameter of seven feet. The most con- 

 spicuous part of this creature, as it floats in the sea, is its great 

 violet-coloured disc, the edges of w'hich are moved slowly up and 

 down as it swims along. In the centre of this disc below, pro- 

 jects the proboscis or external stomach, furnished with a profusion 

 of filmy fringes hanging at the extremities of the four lateral 

 processes into which its free end is divided. From the margins 

 of the disc float backward innumerable long reddish tentacles 

 armed with urticating thread cells, which paralyze any little 

 animal they may touch, and enable it to be drawn into the mouth. 

 These tentacles are often several feet in length. Between the 

 tentacles and the base of the probocis, when the creature is 

 mature, may be seen four great ovaries loaded with yellowish 

 eggs. The eyes and ear-vesicles, each eight in number, are placed 

 in notches in the margin of the disc, while circulation and respira- 

 tion are provided for by a network of vessels ramifying through 

 the disc. Though these animals are as tenuous as jelly, and 

 contain very little solid matter, their organs are of singular 

 complexity, and the body consists of several layers of cellular and 

 fibrous tissues. The reproduction of the Cyanea, as described by 

 Agassiz, forms an interesting example of the changes through 

 which animals of this type pass in attaining to maturity. The 

 eggs are hatched into ciliated embryos which swim freely. These 

 attach themselves to the bottom, and are developed into little 

 bydroids, with tentacles in fours and multiples of four (Fig. 66 a), 

 and which have the power of increasing by gemmation. From 

 this stage the young animal passes by a transverse fission into a 

 sort of jointed form (the Strobila. Fig. 66 b), and this, breaking 

 up into separate segments, produces free swimming discigerous 

 animals, formerly known by the name oi Ephyra, and which are 

 the young of the Cyanea. Thusi each animal passes through four 



