AND ITS ALLIES. 217 



They have prominent shoulders on the inner side at the base. 

 They diverge and taper from the base, and are either outcurved 

 or incurved at the tip, or else somewhat undulate. The longest 

 spurs which I have measured were 75 /x in length. 



Toes. — The ultimate foot-joint, which bears the toes at the 

 extremity, is long and slender. It acts as a sheath for the toes. 

 The toes are all very slender, and consist of a larger and a 

 smaller pair. The long pair are two-jointed, the shorter doubt- 

 fully so. The unusual position of the toes, all close together 

 at the end of the joint, makes the distinction of dorsal and 

 ventral pairs less obvious than in other Philodinae (Fig. 25). 



By analogy with other Bdelloids the long toes would be 

 ventral, or terminal. 



The shorter toes are extremely small, and are so nearly 

 between the longer ones that their position offers no evidence 

 as to whether they are dorsal or ventral. 



Philodina aculeata, Ehrenberg. 



1830. Ehrenberg (6) p. 49 (name only). 



1831. Ehrenberg (7) p. 148 (description). 

 1838. Ehrenberg (8) p. 501, Plate 61, Eig. 9. 



Ehrenberg's diagnosis, 1831 (7), p. 148, is in the following 

 *fcerms : " Langendurchmesser ^_- i.'" Korper gestreckt, blass 

 gelblich. Mittelkorper mit weichen Stacheln oder Hornchen 

 besetzt, welche das Thierchen willkiirlich aufrichten kann. 

 Augen rund. Sporn mit kugelformigen Ende." 



In that description the only character of importance in dis- 

 tinguishing this from other species is the possession of spines. 

 The description would embrace also Bryce's P. spinosa ; but 

 as Ehrenberg defined the genus as having dorsal eyes, that 

 species is separated by the lack of eyes. 



The figure shows an animal possessing as many as twenty-seven 

 spines, two of which point forward, the others backward. 



I do not know that the animal figured by Ehrenberg has been 

 seen by any subsequent observer. 



Authors who refer to and figure the numerous spines, as 

 Dujardin (4) who says the animal is " tout herisee d'epines," 



