APHANIPTERA. 27 



lip has four setaceous hairs upon its under surface. On the dorsal 

 surface of the head we must be careful to note the curious structure 

 known as the " pointe frontale," so well described in Kunckel's 

 paper. It is present in the young larvae, and may be seen prior to 

 its exit from the egg. It is a yellowish-brown, horny plate, and 

 seems to vary in shape in the different species of fleas. This appears 

 to have been first noticed by De Geer.* 



This little corneous plate is placed in a slight depression of 

 the head, and ends in front in a sharp point : the figure will, 

 however, explain best its general shape and appearance in the 

 species of Pulex; namely, P. felis {vide Fig. i). It must be 

 noticed that this structure is only found in the young larvae. It is 

 possibly an organ used to rupture the egg membranes, and thus 

 release the larva. It is no doubt the homologue of the "dorsal 

 plate" found in other insects, so fully described by Kowalevsky,t 

 and again by Dohrn,J who says it is formed from a thickening of 

 the serous membrane which covers the dorsal surface ; this differs, 

 however, from our "pointe frontale" by becoming formed into a canal 

 and then into a tube. This frontal plate, seen in embryo fleas and 

 in Pe7itato7nes, in the Phryga?iidce, and as the so-called " dorsal 

 plate" of Bydrop/iilus, etc., is also, according to Kunckel, homo- 

 logous to a piece which, if it is developed, exists in the front of the 

 larvse of Crustacea, the Zo^a of Caficer mcefias and Pagures and 

 Porcellanes, of young lobsters, etc. 



M. Balbiani also notices a curious point in the frontal region of 

 young PhalangidcB^% which he regards as the analogue of the 

 appendages found on the dorsal surface in other Arthropods. We 

 may also note the antennae situated on the dorsal surface of the 

 head. They are composed of three joints : the first being rounded, 

 and bearing a few protuberances ; the second is cylindrical, and ends 

 in tentacular-like processes ; from this proceeds the third joint, 

 which is small and pointed. 



The Alime7itary Ca?ial. — This is easily seen in living larvae, owing 

 to their transparency. Two small elongated salivary glands open 

 into the pharynx, which is followed by a short and swollen (zsophagus, 

 which gradually narrows as it passes into the chylific ventricle; this 

 part of the digestive track is large and elongated, its posterior end is 



* De Geer, " Memoires pour servir a I'Histoire des Insectes," 1778- 



t " Embryologische Studien an Wiirmern u. Arthropoden." Mem. Ac. Imp., 

 Petersbourg, S. vii., vol. xvi., 1871. 



+ " Notizen zur Kenntniss d. Insectenentwickelung." Zeitschrift f. wiss. Zool., 

 1876. 



§ "Memoire sur le Developpement des Phalangides." Ann. Scien. Nat., vol. 

 xvi., 1872. 



