DEVELOPMENT OF EGGS. 123 



by HerokU on the cp-gs of the jiarden spider (Epeira 

 (iKuloua), to which we ronncilv alhidc d. He divides 

 the |)i()cess of iiatehiiig into twelve periods, according 

 to th(! profjiess of development. This progress is not 

 measured by time, as has been done in experiment- 

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

 \vhich is composed of minute granules, when jilaced 

 in a due temperature, begins to expand towaids the 

 e.\tremity of the egg, till it takes the form of a comet, 

 whose nucleu.-^ is the centre of the germ, and whose 

 tail* consists of transparent globules. On continuing 

 to expand, or rather to dis[)erse its grannies, they 

 appear to be decomposed into imperceptible mole- 

 cules, producing a sort of translucent clond, 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 aecumidatf s round the centre of the 

 germ, assumes a pearly aspect, and becomes solid and 

 0|)aqae. This is the rudiment of the embryo spider, 

 the outline of whose head and body becomes appa- 

 rent, occnpying a little more than a fourth of the tgg. 

 At first this embryo appears homegeneous, 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 termed. The whole secns 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 Gecr, 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 Geuer. Aranearum in Ovo. 



