486 Alice M. Boring 



head, the head forms by condensation of the chromatin (Figs. 44 

 to 47), passing through one rather diffuse stage (Fig. 46). 



Vanduzea arcuata 



Vanduzea arcuata was found in abundance on the locust trees 

 near Cold Spring Harbor in June. The spermatogonial plates 

 show 17 chromosomes, varying in size (Fig. 48). It is not possible 

 to arrange them all in pairs, but at least two large pairs are well 

 marked (a^ and a.y, b^ and bn). In the growth stage, the odd chro- 

 mosome appears as a long, darkly-staining body, without a smooth 

 contour. It is at first bent upon itself in different forms (Fig. 49), 

 and later lies at full length along the nuclear membrane (Fig. 50), 

 resembling the same stage in Entilia sinuata (Fig. 15). In the 

 equatorial plate of the first spermatocyte division, there are 9 chro- 

 mosomes, two of which are larger than the others (Fig. 51, a and 

 b), corresponding to the four large ones in the spermatogonial 

 plate; a is slightly larger than b just as a^ and a^ were slightly larger 

 than b^ and /?,. This point certainly counts as evidence that each 

 spermatocyte chromosome represents not an mdefinite segment 

 of the spireme, but two individual spermatogonial chromosomes. 

 The odd chromosome can be recognized by its eccentric position. 

 Fig. 52 shows all the chromosomes but x in metakinesis, and in 

 Fig. 53 X is passing to one pole undivided. Figs. 54 and 55 show 

 variations in the position of x in anaphase; it does not always lag 

 behind, but may even precede the other chromosomes to the pole. 

 The second spermatocyte equatorial plates, containing 9 and 8 

 chromosomes, respectively, are shown in Figs. 56 and 57. Each 

 has one large chromosome a, one not quite so large b, and six small 

 ones of about the same size. Fig. 56 has a ninth chromosome of 

 intermediate size which must be the odd chromosome, as .v in the 

 first spermatocyte plate has a correspondmg mtermediate size 

 (Fig. 51). All the chromosomes divide in this division, including 

 the odd one, as is shown in all of the lateral views of the metaphase 

 (Fig. 58) and of the anaphase (Fig. 59). Half of the spermatids 

 contain the odd chromosome, and half do not (Figs. 60 and 61). 



