222 J. MURRAY ON PHILODINA MACROSTYLA, EHR., 



Variety. — The spines are pairs 2, 4, 5, and 6. They have 

 broad expanded bases and short blunt tips. The 6 th pair are 

 low cones, almost hemispheres (Figs. 13, 14). 



Variety. — The spines are also pairs 2, 4, 5, and 6. They are 

 reduced to mere hemispheres, with no trace of narrowed apical 

 portion (Fig. 11). 



Spines fewer than 8. 



Forms having six, four, and two spines have also been observed, 

 thus completing the gradation from the most spiny forms to 

 P. macrostyla, and rendering it doubtful whether the two species 

 can be maintained. As both species have varieties, or perhaps 

 merely states, corresponding to Gosse's tuberculata, their 

 discrimination requires care. On several occasions animals 

 which appeared to be typical tuberculata were found, when 

 the viscous secretion was rubbed off, to be P. aculeata. 



Of the forms having less than eight spines no detailed studies 

 are available. The spines of the four-spined form were the 2nd 

 and 4th pairs. 



Philodina macrostyla, Ehrenberg. 



Ehrenberg, C. G. — " Die Infusionsthierchen als vollkommene 

 Organismen," Leipzig, 1838, p. 501, Plate LXI. fig. vii. 



Ehrenberg's diagnosis is as follows : " Ph. alba, laevis, ocellis 

 oblongis, pedis corniculis basalibus praelongis." He found the 

 animal near Berlin, and noticed that there were three teeth in 

 each jaw, and remarked on the correspondence with P. aculeata 

 in this character. He speaks of a respiration-tube, thickened 

 at the anterior end and ciliate (antenna?). 



This rather meagre description is still sufficiently distinctive. 

 A Philodina with very long spurs, three teeth, and oblong eyes 

 can only be P. macrostyla among known species. The only 

 other species having these characters is P. aculeata, and it is 

 distinguished by its spines. 



Ehrenberg gives the length of the animal as Jth of a line, 

 and the length of the egg as ^-th of a line. 



The last statement requires consideration, as all the species 

 of the group we are dealing with are supposed to be viviparous. 



