516 



development we know that it is ten (one half the somatic number). 

 These split segments elongate and become much thinner, and the 

 halves separate, except at the ends, and become twisted around each 

 other (Figs. 2, 3, and 4). It is at this and the succeeding stage that 

 the difficulty of following the process in any of the Hemiptera appears ; 

 the segments becoming so long and the chromatin so scattered as to 

 almost entirely lose any regular form. The distinct rows of granules 

 of which the segments up to this time have been composed, now be- 

 come somewhat broken down and diffuse and the segnient assumes 

 the shape of two Vs, joined together by their free extremities (Fig. 5), 

 and composed of irregular masses of chromatin which is generally 

 spread out so diff"usely that it is only with difficulty that its arrange- 

 ment in this form can be made out. The space enclosed between the 

 two Vs is, I believe, the original longitudinal split; the apices of the 

 Vs are the ends and the extremities of their legs are the middle points 

 of the original segments. The bend at these middle points therefore 

 represents a transverse division and each segment represents a tetrad, 

 formed by two divisions at right angles to each other ^). 



Fig. 5. Fig. 6. Fig. 7. Fig. 8. 



T 



^P 



These bodies now become contracted and condensed (Fig. 7), the 

 intermediate stages varying according to the angle at which the Vs 

 were bent, but the final result in all cases is a very dense body, 

 which, however, clearly shows by its shape (Fig. 8), its four fold value. 

 It is important to notice that these tetrads are not symmetrical but 

 are longer in one direction than in the other (Fig. 8). By following 



1) The two Vs may lie in the same straight line (Fig. 5), or may 

 be bent toward each other so that their apices are almost in contact 

 (Fig. 6). In this case they frequently give the superficial impression 

 that they may be formed by two longitudinal splits, as they are in 

 Ascaris or the flowering plants, and it is possible that an explanation 

 of the great diff'erence between the two types may be sought in some 

 such process as this. 



