134 ANATOMY AND PHYSIOLOGY 



that tribe of sponges, and no other reproductive bodies 

 have, I believe, been discovered in the true sponges ; but 

 in arriving at this conclusion, we must not fail to remember 

 that our knowledge of these animals in the fleshy and solid 

 condition in which they are when alive, is so limited and so 

 few observations have been published regarding them in 

 that state, that we must not attach too great a value to 

 these conclusions. 



In size and form these ovoid vesicles are very similar to 

 the ova liberated from the well-characterised ovaria of other 

 marine species of Spongiadae ; and like them, they present 

 no appearance of a nucleus. They are somewhat irregular 

 in their form, and vary to a slight extent in size; an 

 averaged-sized one measured ^th of an inch in diameter. 

 Fig. 315, Plate XXII, represents a portion of a fibre from 

 a Bahama sponge under a power of 400 linear, and 

 Fig. 316, a part of the same fibre 1250 linear. 



Until very recently our knowledge of the vesicular ovaria 

 of the Spongillidae has been confined to two European 

 species, but Carter, in his excellent account of the Spongillas 

 found in the water-tanks of Bombay, has described several 

 new and interesting varieties of these organs ; and I have 

 also become acquainted with eight new species from the 

 River Amazon, through the kindness of Mr. Bate, and of 

 three un described species from North America, through the 

 kind and liberal assistance of Dr. Asa Gray, Professor 

 Leicley and Professor Dawson, of McGill College, Montreal, 

 Canada. The greater portion of these organs resemble each 

 other very closely in their natural condition, presenting 

 generally the appearance of a more or less spherical coriaceous 

 body, but the structure of their walls, when developed by 

 treating them carefully with hot nitric acid, is so varied 

 and strikingly characteristic of their organic and specific 

 differences, as to render it necessary that I should enter 

 somewhat minutely into their history. Their structual 

 peculiarities naturally divide them into two great groups. 



1st. Those in which the walls of the ovaria are strength- 

 ened and supported by birotulate or unirotulate spicula 

 radiating in lines from the centre to the circumference of 



