ANURIDA. 385 



The view that the ventral tube is an adhesive organ 

 which produces a glandular secretion is also upheld by 

 Haasei, Uzel (38) and Prowazek (21), but these writers 

 regard it as being only a secondary function of the organ, 

 and assert that its principal significance is as an organ of 

 respiration. The thinness of its investing cuticle, and the 

 fact that it always contains a large amount of blood, 

 adapt it for aerating the latter and, therefore, lend support 

 to this contention. 



The two most recent investigators, viz., Willem (27) 

 and Hoffmann (12) both agree in their opinion that 

 though it may fulfil the secondary function of being 

 an organ of respiration, its main function is to 

 serve as an organ of adhesion to aid the animal in 

 climbing. These writers believe that the secretion which 

 moistens the surface of the ventral tube is supplied by a 

 pair of glands situated in the head. The ducts of these 

 glands were first shown by Fernald to open by means of a 

 small pore into the commencement of the ventral groove. 

 Willem and Hoffmann believe that the secretion flows 

 down the ventral groove and reaches the ventral tube and 

 bathes the surface of the latter. The observations of 

 these writers are confirmed in the case of Anurida in the 

 succeeding chapter in this Memoir. By keeping various 

 Collembola in a damp chamber, and observing them 

 climb steep and smooth surfaces, it can be made out that 

 the primary function, at any rate, of the -ventral tube is 

 that of an organ of adhesion. The present writer believes 

 that it also plays an important part as a respiratory 

 organ. Both Willem and Hoffmann regard the modified 

 hypodermis cells lining the ventral tube (h.c. in fig. 21) 

 as being simply ordinary hypodermis cells which have 

 assumed an unusual form; while on account of their large 



\ Die Abdominal -anhange der Insekten, Morph. Jahrb., 1889. 

 BB 



