OF ARTICULATA. 301 



from the spiders, which possess four pairs of legs. In addition 

 to these there are two other characters which, taken in connec- 

 tion with those just mentioned, would, did we not know its 

 origin, vindicate the claim of this embryo to be classed with the 

 Insects proper as contradistinguished from the Spiders. I mean 

 the isolation of the head (k) from the rest of the joints, and the 

 distinct, tenfold jointed division of that part of the body which 

 lies behind the legs, and corresponds to the abdomen (d l to d M ). 

 It is here that we see for the first time the beginning of the 

 change in the relative position of front and back which I hinted 

 at just now. This is indicated at two points, and in two sepa- 

 rate ways, namely, by the elevation of the head (k) from the 

 retroverted position in which it laid at the last stage, (fig. 200,) 

 and by a backward folding of the end (fig. 201, d lo ) of the tail 

 so as to bring it down upon the preceding joints. 



The meaning of these movements on the part of the head 

 and tail are fully explained in the next phase, (fig. 202,) where 

 we find the tail (tl) completely doubled 

 under the body, the head (k) standing 

 out as a distinct division, and the back 

 (y] projecting above the rest of the 

 body and occupying the region for- 

 merly filled by the upturned abdomen ; 

 that is to say, the body has completely 

 reversed its relations to the shell in 

 which it is enclosed, by changing from 

 its former retroflexed condition to a conduplicate position. In 

 addition to the increased elongation of the legs (e,/, g] and the 

 jaws (6, c) and feelers, the complete formation of the rings of 

 the abdomen, (d 1 , tl,) and the appearance of a group of eye- 

 Fig. 202. The same as figs. 108 to 201, but more advanced in development. 

 220 diam. The position is reversed by doubling the tail (//) under the body, k, 

 k 1 , the right and left halves of the head ; 0, the eye ; ?/, the tail ; e/ 1 , the first 

 joint of the abdomen; ft, the upper, and c, the lower jaws; e, f, g, the legs; y. 

 the remnant of the yolk, on the back ; h, A 1 , a furrow in y where the heart de- 

 velops. From Zaddach. 



