338 PLATE XOI. 



rated from that species. The mode of disposition of 

 the skeleton spicula in the two species is strikingly 

 different. In L. botryoides they very closely approach 

 regularity of arrangement; while in L. Somesii, they 

 appear as if felted together, so that their radii in 

 crossing each other are bent and distorted in various 

 directions, so that although in size and proportions the 

 spicula of the two species closely resemble each other, 

 the regularity in the form of the one species and the 

 distortions of the radii of the other readily discriminate 

 them, even when separated from the parent sponges. 

 The total absence in the skeleton of L. botryoides, of 

 the long, slender, acerate spicula, so abundant in L. 

 Somesii, also greatly aids us in their discrimination. 

 The spicular triradiate internal defences of the two 

 species also differ essentially in form and mode of 

 disposition. In L. Somesii, the spicular ray is com- 

 paratively short and straight, and is projected at about 

 right angles to its triradiate base ; while in L. botryoides 

 it is much longer in its proportions, and is curved in 

 the direction of the terminal orifice of the sponge. 



The figure 1, Plate III, of Leucosolenia botryoides 

 representing a specimen from Shetland is so exceed- 

 ingly like in its external characters to the young state 

 of Leuconia Somesii, that I was induced to re-examine 

 it microscopically, and I have satisfied myself that 

 it is truly Leucosolenia botryoides. This striking simi- 

 larity of the young state of the former species with the 

 more than usually developed condition of the last 

 named one, strongly illustrates the inutility of depend- 

 ing on external form as a specific character without 

 careful reference to their anatomical structures. 



My friend, Mr. H. Lee, in his description of this 

 sponge in 'Land and Water,' for September 29th, 

 1873, p. 445, gives some interesting notes regarding 

 the growth, development, and decease of this species. 

 He states "the sponge above described increased in 

 diameter for six months from its first appearance, and 

 then gradually ceased to spread, but continued slowly 



