158 Edmund B. Wilson 



I Individuals having twenty-one spermatogonial Chromosomes^ 

 including an unpaired Idiochromosome. Small Idiochromo- 

 some and Supernumeraries absent 



To this group belong only the specimens, all males, collected by 

 Montgomery at West Chester, Pa., of which I have examined nine 

 individuals, all of w^hich have essentially the same characters.'' 

 Montgomery ('01) originally described these forms as having 22 

 spermatogonial chromosomes but subsequently ('06) corrected this 

 to 21, describing the phenomena as agreeing in all essential respects 

 vv^ith those seen in Anasa and other coreids. A study of the orig- 

 inal preparations has enabled me to confirm this later account in 

 every essential point. After the synizesis or contraction phase of 

 synapsis (as in all individuals of the genus) the ordinary chromo- 

 somes appear in the form of rather delicate spireme-like threads, 

 longitudinally spHt. In later stages of the grov^th-period they 

 shorten, become irregular, lose their staining capacity, and assume 

 the vague, pale condition characteristic of so many other forms. 

 In the early prophases of the first division they become more defi- 

 nite, stain more deeply, and appear as coarse longitudinally split 

 rods that often show an indication of a transverse division at the 

 middle point, or in the form of the double crosses as described by 

 Paulmier in Anasa ('99). In the later prophases they condense 

 still further to form nine compact bivalents which finally arrange 

 themselves in a more or less regular ring. The equatorial plate 

 of the first division always shows in polar view 11 chromo- 

 somes (Fig. 3, a, b. Photo l). In the most typical case the univa- 

 lent idiochromosome lies outside this ring, but it sometimes lies 

 in or inside it. The small m-chromosome bivalent is always near 

 the center of the ring. In side view the larger bivalents are either 

 dumb-bell shaped or more or less distinctly quadripartite, in the 



^ These were taken from magnolia trees. In the summer of 1907 I collected in the same locality 

 two males and three females, all from blackberry bushes. To my disappointment, these differ from 

 Montgomery's specimens, one male having 22 spermatogonial chromosomes, the other 23; while the 

 ovarian cells have in one female 23 and in theother two 24 chromosomes. It is possible that a different 

 species fell into Montgomery's hands, perhaps an introduced form; but both the structure of the testis 

 and the character of the chromosome-groups agree so exactly with my own material that I now believe 

 that Montgomery's identification was probably correct. 



