418 Dr. Johnston's Contributmis to the British Fauna. 



doubt concerning what he may intend, but in Jassa pulchella the inferior 

 antennae are the longest, and are said to be leg-shaped, a form which 

 those of Gamm. spinipes have not, if I have a correct idea of what is meant 

 by that term. His character, " thumb of the second pair of legs with 

 " its internal edge notched at the base," is unintelligible, for it seems to 

 imply that the hand is didactyle, while in the definition of the genus it is 

 stated to be monodactvle. 



Alcvonium hirsutum. 



(Fleming, Brit. Anim, p. 517.) 



Desc. Polypidom variously branched, often proliferous, sometimes 

 subcylindrical, commonly flattened and palmate, of a dirty straw-yellow 

 colour, often partially stained with red, and (always ?) spotted, the spots 

 yellowish, numerous, circular, and irregularly disposed. It is thickish, 

 and somewhat cartilaginous, and to the naked eye resembles a compact 

 sponge. When viewed through a common magnifier, the surface is seen 

 to be covered with close-set conical transparent papillse, each of which 

 is a cell containing a Polype with 16 equal long fihform tentacula. ar- 

 ranged in a circle. 



I have at present (February 3rd.) at least 50 specimens before me of 

 various sizes, and all of them are marked with the yellow spots mentioned 

 in the description, and which are about ^V of an inch in diameter. 

 They are placed in the thickness (not on the surface) of the Polypidom, 

 and on breaking it we can readily separate them with a needle. Each 

 then appears to be made up of ten or more small globules of a milk- 

 white colour, and opake. When magnified, I was surprised to find them 

 moving in the glass of water with great rapidity, and in all directions. 

 This progressive motion is very obviously effected by the ceaseless play of 

 a fine thick fringe of ciliae, which surrounds two-thiids of their circum- 

 ference. They have also a rotatory motion ; and a globule may be seen 

 moving forward and whirling on its own axis at the same time. 



On the nature of these bodies I will not decide. They are too large 

 to be considered as ova, and they resemble very closely the Entomostraca 



