348 INSECTA. 



the sternal part of each segment, and communicate internally with a 

 double series of pneiunatic sacs strung together like a rosary, extend- 

 ing along the body, from Avhich proceed tracheal branches that ra- 

 mify over the other organs. According to an observation of Straus, 

 the sacs or vesicular trachea are not, as usual, connected Avith each 

 other by a principal trachea. 



In the environs of Pisa, where M. Savi collected the preceding 

 facts, the nuptial season of the common lulus commences near the 

 end of December, and terminates about the middle of May. The 

 male organs of copulation, in this species, are situated under the 

 sixth segment, but they do not ajjpear in this form till the individual 

 has attained the one-third of its full size ; until this epoch, that place 

 is occupied by a pair of feet (the fifteenth), which is always found 

 there in the females ; in the latter, the orifice of the sexual organs 

 is between the first and second segment. Some female Glomeres and 

 luli, behind the origin of the second pair of feet, exhibit two convex 

 mammillae, which appear to characterize this sex; that of the males 

 also consists of two mammillae, but each of them is terminated by a 

 scaly and twisted hock. These insects, in coitu, erect the anterior 

 extremities of their bodies, and place them in contact, face to face, 

 twining round each other inferiorly. The body of the new-born ani- 

 mal is reniform, perfectly smooth, and destitute of appendages. 

 Eighteen days after, it undergoes its first change, and then for the 

 first time assumes the form of the adult, still, however, having but 

 twenty-two segments; the total number of feet also amounts to twenty- 

 six pairs. Savi appears to contradict the assertion of De Geer, who 

 says that he only found three pairs and eight annuli in the young 

 animal — but it is certain that this change of which Savi speaks is 

 really the first ; and should we not, on the contrary, rather presume 

 that these young individuals do not suddenly pass from a state in 

 which they exhibit no locomotive appendages to one where we find 

 them possessed of twenty-six pairs, or, in a word, that previous changes 

 of tegument, which have escaped the notice of Savi, have taken place 

 and successively developed this number of feet ? Do not the obser- 

 vations of the Swedish Reaumur confirm these gradual transitions ? 

 Be this as it may, the first eighteen pairs of feet, according to Savi, 

 alone serve for locomotion ; at the second change we observe 

 thirty-six pairs, and at the third, forty-three ; the body then consists 

 of thirty segments. Finally, in the adult state, the male has thirty- 

 nine, and the female sixty-four ; two years afterwards they again 

 experience a change, and then only do the genital organs make their 

 appearance. From the moment of their birth, which occurs in March, 



