70 THE SALTATORIAL APPENDAGE. 



saillante, multiarticulee," while in the species I have 

 examined it is horny, and has only two segments. 

 Thus, in Tomocerus longicornis it consists of a basal 

 portion and two short arms, each with four teeth on 

 the outer margin. It only exists in certain genera. 



The great saltatorial appendage is attached in 

 most cases to the underside of the penultimate (PL 

 VIII, figs. 2 and 3 ; PL XYI. See also Pis. LVII— 

 LXI), but in Poclura and Achorutes (Pis. XL, XLI) to 

 that of the antipenultimate segment. It is not, there- 

 fore, in fact, homologous in these groups. Nor is it 

 strictly correct to call it, as Nicolet and others have done, 

 a tail. It consists of a basal segment and two append- 

 ages, which are sometimes 2-jointed and sometimes 

 consist of a single piece each. This organ has gene- 

 rally been considered as peculiarly characteristic of 

 the CoLLEMBOLA, but, on the contrary, it is altogether 

 wanting in the Lipuridce and Anouridce, which in con- 

 sequence are non-saltatorial. Moreover, as already 

 mentioned, although a saltatorial appendage occurs in 

 all the Smynthuridce, Painriidce, Degeeridce, and Podii- 

 ridce, the saltatorial organ of the latter family is not 

 really homologous with that of the majority of the 

 group. In fact, therefore, we find among the Collem- 

 BOLA subabdominal appendages attached to at least 

 three segments, viz. the third, fourth, and fifth ; but 

 whereas that of the fourth segment has disappeared in 

 Oi'chesella, Tomocerus, &c., that of the fifth, on the 

 contrary, is wanting in Podura, &c. Hence we appear 

 to have indications of a time when each segment had a 

 pair of ventral appendages. 



The saltatorial organ often presents good specific 

 characters, and in some species is provided with tenent 

 hairs. 



It is usually turned forwards. In Orchesella, Tomo- 

 cerus, and the allied genera, it lies in a central furrow, 

 and the terminal branches reach about to the poste- 

 rior end of the thorax, while in Podura and Achorutes 

 the organ is less elongated. The basal portion reaches 



