DEVELOPMENT OF EGGS. 123 



by Heroldt on the eggs of the garden spider (Epeira 

 diadcma], to which we formerly alluded. He divides 

 the process of hatching into twelve periods, according 

 to the progress of development. This progress is not 

 measured by time, as has been done in experiment- 

 ing on the eggs of birds. The germ, or cicatricula, 

 which is composed of minute granules, when placed 

 in a due temperature, begins to expand towaids the 

 extremity of the egg, till it takes the form of a comet, 

 whose nucleus is the centre of the germ, and whose 

 tail* consists of transparent globules. On continuing 

 to expand, or rather to disperse its granules, they 

 appear to be decomposed into imperceptible mole- 

 cules, producing a sort of translucent cloud, through 

 which the globules of the yolk may be distinguished. 

 The place which the germ previously occupied ap- 

 pears as a single transparent point. The cloudy 

 matter next accumulates round the centre of the 

 germ, assumes a pearly aspect, and becomes solid and 

 opaque. This is the rudiment of the embryo spider, 

 the outline of whose head and body becomes appa- 

 rent, occupying a little more than a fourth of the egg. 

 At first this embryo appears homcgeneous, but by and 

 by four little archlets are seen, which are the rudi- 

 ments of the legs, and at the same time the outlines 

 of the mandibles are formed. The whole seems to 

 derive nourishment from the yolk, in which it is rooted 

 as a parasite plant upon a tree. When the embryo 

 spider is near its exclusion, it completely fills the inte- 

 rior of the egg, the shell of which moulds itself close- 

 ly around the body, and it looks like the nymph of a 

 beetle.* When sufficiently developed, it makes a rent 

 in the shell, as was first observed by De Geer, oppo- 

 site the breast, through which it pushes its head, and 

 successively disengages its body; but the shell still 

 envelopes the legs and feet, and it is not without a 



* Heroldt, Exercit. de Gener. Aranearum in Ovo. 



