234 HALF-AN-HOUR 



To make the series complete, slides would also be necessary to 

 show, by dissections, the skin, the trophi, and the limbs, in the 

 various modifications. 



Spicules of Tethea cyncurium. — Tethea is a sponge, of a 

 rounded form ; some specimens reach the size of a cricket-ball, or 

 larger ; others do not go beyond a large marble in size. It differs 

 from most sponges in its solidity, and the possession of an outer 

 skin, so that it might be likened in appearance to some of the 

 Puff-balls. I remember the delight with which Bowerbank showed 

 a number of specimens that had been obtained by deep-water 

 dredging off the Shetlands a great many years ago. In the "Micro. 

 Dictionary" only two species are mentioned, but I suspect there are 

 more known now. The similarity of these Sponge spicules to 

 acicular and stellate raphides will strike the thoughtful observer, 

 and the analogy is neither a fanciful nor a forced one. The stellate 

 ones represent the sphaeraphides so abundant in the Cactaceae 

 especially, and the office of both is partly to give firmness to the 

 soft tissues in which they occur. And some of the large acicular 

 spicules show a laminated growth with central vacuity, such as may 

 be seen in some of the large vegetable hairs ; those on the leaf of 

 the Hollyhock to wit. 



Palsemon serratus jun. — A very interesting slide. I should have 

 liked to have seen some specimens presenting the side-view, others 

 laid on their backs. R. Warington will be remembered as the 

 inventor of the aquarium, through discovering the grand law of 

 the balance of animal and vegetable life. He had a large mass of 

 most careful observations, which he designed to publish. I never 

 knew why this was not done, and fear that by his death they are 

 now lost to science. 



Argas reflexus is figured in the Crochard edition of Cuvier's 

 " Regne Animal." The figure is a beautiful one, and, I believe, 

 correct as far as it goes. I have no doubt in my own mind that it 

 is the large " Tick " which Henry Denny mentions his having 

 found on Pigeons (" Monographia Anoplurorum Britanniae," p. 

 173) ; we must try and trace the specimen to clear up the matter. 

 As they are well known to be parasite on Pigeons, all difficulty is 

 removed as to how they got into the Cathedral (these ticks were 

 discovered by Mr. Jas. Fullagar, of Canterbury, in the Cathedral 

 of that city), since we are told that jackdaws and pigeons had 

 roosted there from time immemorial (Fullagar in "Science Gossip," 

 June, 1874, p. 121). It would be satisfactory to know more of the 



