522 



SCIENCE. 



[N. S. Vol. XXIII. No. 588. 



and A. edentula, because of their transpar- 

 ency, are very suitable objects for the study 

 of maturation, fertilization and early cleav- 

 age. The maturation divisions can be fol- 

 lowed with ease and even the chromosomes 

 can be made out as highly refractive bodies 

 in the equator of the spindle. A study of 

 the approach of the male and female 

 pronuclei confirmed the observations of 

 Lillie on sections of the JJnio egg regarding 

 the disappearance and reappearance of the 

 central sphere. The central sphere at the 

 side of the male pronucleus disappears as 

 the two pronuclei approach each other and 

 for a considerable period there is no sign 

 of a central sphere in the egg. Then a 

 central sphere forms in connection with 

 each pronucleus and astral radiations ap- 

 pear around it. The two central spheres 

 thus produced serve as the centers of the 

 first cleavage spindle. 



On the Interpretation of the Maturation 

 Chromosomes of the Orthoptera: C. E. 

 McClung, University of Kansas. 

 A very general interest centers about the 

 interpretation of the chromosomes of the 

 grasshoppers since every possible deriva- 

 tion of the tetrads has been described as 

 showing itself in their spermatocytes. Thus 

 Wilcox detects a double cross division, de 

 Sinety a double longitudinal one, while I 

 and my students are convinced that in most 

 of the tetrads there are present for the 

 first spermatocytes a plane of longitudinal 

 cleavage and for the second a cross division. 

 Montgomery, from a brief study of one 

 species, argues for a cross division in the 

 first spermatocytes and a longitudinal in 

 the second. From the fact that all these 

 interpretations have been based upon prac- 

 tically the same material, it is important to 

 determine which is the correct one, for it 

 will materially strengthen the assumption 

 that this is the type that is generally' prev- 

 alent. I have recently gone over a large 



number of species of Acridids and am con- 

 vinced that my early conception of the 

 tetrad as a rod split lengthwise and again 

 at right angles to this, with the mantle fibers 

 attached at the level of the cross split, is 

 the correct one. These two planes of divi- 

 sion have been found in the very early pro- 

 phases and traced through the two sperma- 

 tocyte divisions. The ring figures present 

 indisputable evidence that the first cleavage 

 of the rod is along the length of the chro- 

 matin thread. These facts are demon- 

 strated by a large series of photomicro- 

 graphs. 



The Chromosome Complexes of Hespero- 

 tettix speciosus and H. viridis: C. E. 

 McClung, University of Kansas. 

 As I reported at the preceding meeting 

 of the society, the genus Hesperotettix has 

 a peculiar grouping of the chromosomes 

 that characterize the Acrididae. This mani- 

 fests itself particularly in the multiple 

 chromosome which is constituted of one of 

 the large tetrads and the accessory chro- 

 mosome. The two species of the genus 

 show differences in size and shape that are 

 striking and unmistakable, but which are 

 not easy to describe. A full series of illus- 

 trations will be presented in a subsequent 

 paper. Accompanying the chromosomic 

 differentiation there is also one of the 

 spindle of the first spermatocyte. This in. 

 H. speciosus is long and full while in H. 

 viridis it is short and weak. In another 

 species, H. pratensis, that is just being 

 taken up for study, the same elements are 

 characteristically different from the other 

 two species, but have the generic features 

 equally well marked. 



Further Observations on Artificial Par- 

 thenogenesis: George Lefevbe, Univer- 

 sity of Missouri. 

 In a former communication'- some pre- 



' Science, N. > S., Vol. XXI., No. 632, p. 379,. 

 March 10, 1905. 



