130 



PENTA.STOMIDAE. 



The early shedding of a cuticular integument within the egg, which must be 

 regarded as a moult, recalls the formation of the deutovum-membrane in the 

 Acarina (p. 96) ; similar processes occur also in the Crustacea (Vol. ii., p. 118). 



Before the dorsal cone is broken through — i.e., before the cuticular 

 envelope is completely detached from the embryo — two pairs of 

 truncated appendages have developed on the ventral side. These 

 are limbs on which claws soon appear. A narrower posterior portion 

 — the so-called tail — has, previous to this, become marked off from 

 the compact trunk (Fig. 58 A and B), to the ventral surface of 

 which it is applied. This caudal appendage is characteristic of the 

 embryos of a few species of Pentastomum. In P. taenioides it is 



3k- 



h< 



&!._,# 



eh- 



Fig. 5S. — Embryos in the egg-integuments and free larva of Pentastomum taenioides (after 

 Leuckart). dst, stigma of gland ; eh, embryonic integument; /, "facet"; h, egg-integu- 

 ments ; m, oral plate ; p 1 and p„, truncated limbs ; rk, dorsal cross (dorsal organ) ; rz, dorsal 

 cone ; s, caudal appendage. The boring apparatus of the embryo is not shown. 



somewhat large (Fig. 58 B and C), while in P. proboscidmm it 

 is merely a small bifid appendage (Fig. 59, s). The embryo of 

 P. oxycephalum has no caudal appendage, but presents a round 

 posterior extremity. In this form the embryo leaves the egg (Van 

 Beneden, Schubart) ; it is therefore very unlike the parent in 

 shape, and has to pass through radical transformations before 

 attaining the adult form (Leuckart). 



The Larval Development. 



The further course of development is marked by the transference 

 of the eggs into the intermediate host and the development of a 



