172 Transactions of the Society. 



Sub-Class HELIOZOA. 



Order Desmothoraca. 



Hedriocystis spinifera sp. n. 



Capsule very minute, transparent, thin, colourless or of a pale 

 yellow, spherical, having numerous facets more or less regularly 

 polygonal, of usually five or six sides, with raised borders from 

 the junction of many of which arise slender spines ; no pedicel 

 observed ; body spherical, nearly filling the capsule ; plasma bluish 

 in colour, granular ; nucleus single, placed sub-centrally ; a single 

 contractile vacuole normally present ; pseudopodia long, radiating, 

 straight, tenuous ; habit solitary. 



Diameter of capsule, 8-12 /x. 



HaMtat. — Wet moss. 



Locality. — Isle of May, Scotland (Brown). 



The other fresh-water members of this genus {H. jJellucida 

 H. & L., and ff. reticnlata Penard) are provided with a stalk or 

 pedicel, but so far no individuals of this species have been found 

 with this appendage. In collecting from a material like wet moss 

 they may easily have been broken off. 



In the well-known genus Clathrulina the chitinous capsule 

 is a reticulated framework, also spherical in shape, the openings 

 in which are of such a comparatively large size that a mere 

 latticework separates them from one another ; but in the genus 

 Hedriocystis the test is continuous, the pseudopodia passing through 

 a mmute pore in the centre of each facet. The presence of these 

 pores can only be recognized when the animal is alive, by the 

 pseudopodia emerging from them ; but in specimens treated with 

 sulphuric acid Penard observed small bubbles of gas escaping, by 

 which their presence was indicated. 



The capsules in this genus are so transparent and colourless that 

 only the thickened portions can be distinguished. 



The smaller size and the presence of spines at the angles of 

 the facets of the capsule distinguish this species from H. reticulata 

 Penard (about 25 /i diam.), which likewise has only been recorded 

 from one locality in the British Isles, namely, Craigcaffie, 

 Scotland (Brown, in " Scottish Naturalist," 1916). 



H. pellacida H. & L. has not till now been recorded from 

 the British Isles ; it is distinguished by the small pore in each of 

 the facets being surrounded by a conical boss or nipple. 



Propagation by means of division taking place within the test 

 has been observed in H. reticulata, but it is not known how the 

 individuals so formed escape from the capsule. . 



The author is much indebted to Mr. G. H. Wailes for assistance 

 in drawing up the descriptions of these species. 



