4l6 TRANSFORMATIONS OF INSECTS. 



wriggling and much trouble to get out of the old skin. When 

 the skin has been got rid of, the singular fact comes to light 

 that another large segment and two more pairs of legs are added, 

 so that the Paiiropiis becomes a ten-legged animal. After a 

 while the insect moults again, and at each change of skin obtains 

 a fresh pair of legs, and at last nine pairs are developed. 



The three pairs of primitive legs so characteristic of the true 

 insects are speedily added to during the growth of the young 

 Juhis, and that this is the case will be gleaned from Newport's 

 description of the Myriapod from its earliest observable state. 



The development of the young Jidus is divided by Newport* 

 into several distinct and well-marked periods. The first period 

 extends from the deposition of the ^gg to the gradual bursting 

 of the shell and the exposure of the embryo within, occupying 

 the space of twenty-five entire days, during which the t.g'g acquires 

 a sensible increase of bulk. 



On the nineteenth day there was a complete alteration in the 

 form of the tgg. It was more obtuse at both ends, and had 

 become much larger, and the outline of the embryo, coiled up 

 within the shell and nearly filling the whole interior, was very 

 distinct, although as yet there were no rudiments of limbs or 

 even of a division o/ the body into distinct segments. On the 

 following day (the twentieth) the outline of the embryo was 

 more apparent, and on its concave or ventral surface there were 

 faint traces of a division of the body into six segments. Up 

 to this time Newport was unable to detect an umbilical cord 

 attached to the embryo. From this time the &gg became larger 

 every day, until the twenty-fifth day, when it was greatly distended, 

 and began to assume a kidney-shaped appearance, and commenced 

 bursting along the back, the back of the white embryo gradually 

 passing through the opening (Fig. l). 



In the second period of development the embryo is exposed 

 to a new medium, and perhaps derives the means of its further 

 growth from external sources, although it is still enveloped in 

 the foetal membranes, and retains its connection with the shell. 



* Quoted from Rymer Jones' article "Myriapoda," in the " Cyclopcedia of Anatomy 

 and Physiology." 



