394 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



researches of Willem go to prove that in the greater 

 number of Collembola (i.e., in the Sminthuridse, the 

 Entomobryidse and in some of tlie Achorutidae) the eyes 

 are constructed on the eueone principle, and he regards 

 them as being incipient compound eves. In several 

 genera of the Aehorutidse (including Anurida) he points 

 out that there is no layer for the secretion of a crystalline 

 cone, and hence he looks upon the eyes of such forms as 

 being ocelli or stemmata. He remarks (27 p. 90): — 

 " La consideration que les ocelles s'observent parmi ]es 

 Podurides, chez des formes animals ou les organes visuels 

 sont manifestement regression, incite a adniettre que ces 

 stemmates sout productions derivees de l'ommatidie 

 eueone par la disparition du systeme lentigene, con- 

 clusion qui accords avec des faits observes par Patten 

 dans le developpement des ocelles de Vesjxi et de larve 

 ii'Acilius, et qui au tori sent a adniettre que les stemmates 

 a deux couches cellulaires de ces Iusectes derivent d'un 

 oeil a trois couches (comme Pommatidie eueone) par 

 l'atrophie ou le developpement incomplet de la strate 

 nioyenne." 



If the extreme simplicity of the structure of the 

 eyes of Anurida is due to retrogression, and is not a 

 primitive character, it lends support to a belief 

 maintained by certain students of the Collembola, viz., that 

 Anurida is, in some respects, a degenerate type. 



The post-antennal organ (Plate I., figs. 4, 5 and 10, 

 Plate III., fig. >\i) is a curious cuticular structure, circular 

 in form and situated one on each side of the Lead 

 immediately in front of each protuberance which bears 

 the ocelli. It consists of a variable number of somewhat 

 triangular bodies, which are in close contact with one 

 another, with their apices directed towards its centre. 

 The number of these bodies varies in different individuals, 



