422 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Sensory organs of varied form are usually present on 

 the ultimate and penultimate segments of the antenna?. 

 An account of these structures is given by Absolon (6) 

 and also by Borner (7). 



The mouth-parts in all Collembola appear deeply 

 insunk within the head capsule ; this condition is a 

 secondary one, having been brought about through their 

 becoming overgrown and partially surrounded by the side 

 folds of the head. Those of Anura are greatly specialised 

 and differ from the mouth-parts of other Collembola in 

 being purely suctorial. In this genus the labrum and 

 labium together form a conical tube, in which the rest 

 of the mouth-parts are contained, the latter being 

 modified into stylets and used for piercing purposes. 



The digestive canal is a simple tube passing from the 



mouth to the anus without presenting any convolutions, 



and this condition appears to be constant in all the genera 



yet studied. The mid-gut of Neelus is remarkable on 



account of its being sub-divided into a series of four 



successive chambers. With the exception of salivary 



glands, no accessory structures are associated with the 



alimentary canal. 



The nervous system appeal's to exhibit very little 



degree of variation throughout the order. 



Special respiratory organs are wanting, except in 



species of Sminthurus, Sminthurides, and in Actaletes 



neptuni Giard ; in these forms tracheae are present. Tracha* 



are well known to be found in Sminthurus, and it is in 



that genus that they are best developed. According to 



Willem, on either side of the body, between the head and 



the prothorax, there is placed a simple stigmatic crypt, 



from which bunches of trachea? arise and are distributed 



to the head, the legs and the abdomen ; * no anastomoses 



* The exact position of the spiracles appears to require further- 

 study. Lubbock and Tullberg maintain they are situated on the 

 head, while Haase states that thoy are placed on the prothorax. 



