As regards the metamorphoses of the embryo, Manson states that for a little while after gaining access to the stomach of the mosquito the embryo undergoes no change (Fig. 40, _a_). In a very few hours changes commence, resulting in wider separation of the outer skin and an appearance of transverse markings on the body within (_b_). In the next stage oral movements occur; the striation becomes more marked, and the outer envelope is cast off (_c_). Then the striated lines disappear and a dotted appearance is substituted (_d_). From this condition the embryo passes to what Manson calls the chrysalis stage, in which nearly all movement is suspended and the large spots gradually disappear (_e_, _f_, _g_, _h_, _i_, _j_, _k_). The tail continues to be flexed and extended at intervals and the oral motions cease. By the close of the third day the embryo becomes much shorter and broader; but the finely pointed tail retains its original dimensions, projecting abruptly from the sausage-shaped body (_m_, _n_). Large cells next appear in the interior of the body, and by a little pressure one may detect indications of a mouth (_o_, _p_, _q_, _r_). At this period the embryo begins to elongate, and at the same time to diminish in width; but the growth takes place chiefly at the oral end of the body. The mouth becomes four-lipped, open, and funnel-shaped, and from it a delicate line can be distinctly traced passing to an opening near the caudal extremity, the tail itself gradually disappearing (_s_, _t_). Speaking of the most advanced stage Manson says:--“A vessel of some sort is seen in the centre running nearly the whole length of the body and opening close to one extremity. This end is slightly tapered down and is crowned with three or perhaps four papillæ, but whether this is the head or tail, and whether the vessel opening near it is the alimentary canal or the vagina, I cannot say.” Now it is quite evident, I think, from Manson’s figures that he has here faithfully represented the head and tail, the former (_u_) to the left, the latter (_v_) to the right. In his _manuscript_ (from which I am now quoting) there is no special reference to these two figures; but it is easy to see that these terminal sections of the body of the advanced embryo closely correspond with the head and tail of the adult worm (_Filaria Bancrofti_). The curved line passing to the left (_u_) evidently indicates the commencement of the partially-formed vagina.