. AND THE DEVELOPMENT OF THE MYRIAPODA. 113 



and perfectly transparent membrane (c), which seemed to contain a clear fluids inter- 

 posed between it and the embryo. This membrane I regard as the analogue of the 

 dninion, the vitelline, or investing membrane of the embryo in the higher animals, 

 and identical with the memhrana vitelU, before described as the proper membrane 

 of the yelk in the Q^g of lulus. It is a shut sac, that completely invests the embryo, 

 except at its funnel-shaped prolongation at the extremity of the body (rf), where it is 

 constricted, and, together with another membrane (e), which in the unburst qq^ is ex- 

 ternal to this, and lines the interior of the shell, assists to form the cord or proper 

 funis {d). The funis enters the body of the embryo at the posterior part of the 

 dorsal surface of the future penultimate segment, where the mucro or spine exists, in 

 the adult animal, and not at the dorsal surface of the thoracic region, as seen by 

 Rathke in the Crustacea. The proper anal or terminal segment (9) is as yet but im- 

 perfectly developed. In the funis (d) I also observed some exceedingly delicate struc- 

 tures that exhibited all the appearance of vessels. They seemed to enter the body 

 by two sets, that were spread over, and entirely lost in the membrane (e). Whether 

 these were, indeed, vessels, or merely folds of the membrane, I am not certain. The 

 membrane (e) in which they appeared adheres closely to the shell, and retains the 

 embryo in connexion with it by means of the funis. In the unburst egg this is also 

 a shut sac, like the amnion, and forms the membrana externa or chorion [?], the second 

 or outer investing membrane of the ovum lining the interior of the shell. 



The detection of these two investing membranes of the embryo in Myriapoda may 

 be regarded with some interest in reference to the analogies which they bear to simi- 

 lar structures in Vertebrata, since they show the persistence of one universal law in the 

 mode of development of the germ. 



On the second day after the bursting of the egg, the segments of the body were 

 more distinctly marked, and the form of the second, the prothoracic segment, was 

 slightly altered, and the rudiments of the legs were enlarged. 



On the third day the embryo had considerably increased in size (fig. 6.), but was 

 still perfectly motionless, and attached to the shell by the funis. This attachment 

 continues for many days, during which the embryo remains partially protected by 

 the two halves of the shell (fig. 5 and 8.), and in so far as it has ceased to derive 

 nourishment from an internal source, although still an embryo, it may perhaps, physio- 

 logically considered, be regarded as placed in the same relative state of extra-uterine 

 existence, as the foetus of the Kangaroo in the marsupium of its parent. When ex- 

 amined at this period in the recent state, all the parts of the body are still indistinct ; 

 but in specimens that have been for some time in spirits of wine, the divisions be- 

 tween the segments aie well marked, and the altered form of the prothoracic segment, 

 with its smooth rounded inferior surface, is well defined. The rudiments of the legs 

 are more developed, but those of the second and third segments less than the fifth ; so 

 that not only at the bursting of its shell, as first noticed by Savi, but also for several 

 days afterwards, the embryo is completely apodal, the future limbs existing only in a 



