May 



1922] 



SCIENCE 



plane of cell division, and that with the constric- 

 tion of the cytoplasm during the division each 

 ring occupies a position betAveen the nucleus of 

 tlie daughter cell and the cell plate. This ring 

 becomes condensed into an irregular disk which 

 lies close to the nuclear membrane, where it re- 

 mains during the intcrkinetic, or so-called resting, 

 stage. On the approach of cell division, the disk 

 breaks up into clusters of vesicles, varying in 

 number from two or three to a dozen or more, 

 which become distributed irregularly through the 

 cytoplasm, but chiefly in regions peripheral to 

 the spindle figure. During the late prophase and 

 early metaphase of nuclear division, the clusters 

 of vesicles with their enveloping finely granular 

 matter are again collected into an equatorial ring. 

 At the end of the second maturation division, 

 which results in the formation of the spermatid, 

 the vesicles, at first small and numerous, consti- 

 tute a thick disk-like structure at one pole of the 

 nucleus. By the time the chromatin has resumed 

 the appearance of a fine network, two things 

 have happened in the disk-like group of vesicles, 

 now become spheroidal; by confluence they have 

 increased in size and diminished in number ; at 

 the same time a differentiation has taken place in 

 them so that a few small centrally-located ones, 

 probably not resulting from confluence, are 

 deeply stainable, whereas the more peripheral and 

 larger ones have become so distended with non- 

 stainable substance that they appear very pale. 

 The confluence of the peripheral pale vesicles 

 continues till there are only two, which are mutu- 

 ally flattened in a plane passing through the 

 center of the nucleus. Each of the two contains 

 a small number of the small deeply staining 

 vesicles. Meanwhile the cytoplasm on the side of 

 the cell corresponding to the vesicles begins to 

 elongate to form the tail. Then the two vesicles 

 move away from the nucleus a short distance and 

 eaeh becomes spheroidal. Between the two ap- 

 pears the axial filament and as the cytoplasmic 

 outgrowth becomes still more elongated, the two 

 spheroidal structures also become elongated in a 

 direction parallel with the axial filament, which 

 they closely invest. The small contained deeply 

 staining vesicles become arranged in a longitudinal 

 row; the wall of the outer enveloping sac dis- 

 appears, setting free the deeply staining vesicles, 

 which now become distributed along the axial 

 filament, and finally break down, furnishing the 

 finely granular envelope enclosing the axial fila- 

 ment. 



Vegetati've types of Datura due to differences 

 ill somatic number of chromosomes: Dr. A. F. 



Blakeslee, Carnegie Institution of Washington, 

 Cold Spring Harbor, L. I., N. Y. Normal plants 

 have 2 n chromosomes in somatic cells. Certain 

 Datura mutants differ in chromosome number 

 from the norm. Of balanced types, with an equal 

 number of chromosomes in each set, forms occur 

 ivith 1 n, 3 n and 4 n chromosomes. Of unhal- 

 anced types^, with an excess or a deficiency of one 

 or more chromosomes in one or more of the indi- 

 vidual sets, forms occur mth such somatic formu- 

 la; as (2n 4- 1) and (4n — 1). These differ- 

 ences in chromosome number, especially in unbal- 

 anced types, cause distinct differences in somatic 

 structure. Several thousand vegetative forms are 

 considered theoretically possible from chromo- 

 somal types already discovered. 



A method for the study of filterable viruses as 

 applied to vaccinia: Dr. W. G. MacCallum and 

 E. H. Oppenheimer, of the Johns Hopkins Uni- 

 versity. Attempts at the isolation of the infec- 

 tive agent in vaccine and smallpox have failed. 

 It can at least be separated from most contam- 

 inating material if it be eentrifugalized in a sus- 

 pending fluid of appropriate specific gravity. The 

 infective material in vaccine lymphs rises to the 

 top in a fluid of specific gravity 1.16 and sinks to 

 the bottom in any fiuid of specific gravity lower 

 than 1.13. 



Continuation report on experiments in epidemi- 

 ology: Dks. Simon" Flexner and H. L. Amoss, 

 Eookefeller Institute for Medical Research. The 

 continuation report on epidemiology relates first 

 to the epidemic disease, mouse typhoid, reported 

 on at the last spring meeting of the academy, 

 and second to an epidemic disease, rabbit septi- 

 cemia, which is not infrequent!}' met with among 

 domesticated rabbits and the nature of the spread 

 of which we have undertaken to study under con- 

 trolled experimental conditions. These two dis- 

 eases represent also two divergent modes of propa- 

 gation of epidemics of disease, namely, by way 

 of the gastrointestinal organs as in mouse typhoid, 

 and through the respiratory organs as in rabbit 

 septicemia. The ultimate purpose of the investi- 

 gation is the securing of precise knowledge which 

 may come to bear on and extend knowledge re- 

 garding the manner of spread and its underlying 

 causes of such epidemic diseases in man as menin- 

 gitis, poliomyelitis, influenza, cholera, etc. 



Beplantation of entire limbs without suture of 

 vessels: Dr. W. S. Halsted, Johns Hopkins Hos- 

 pital, Baltimore, Md. The experiments were 

 made in the effort to ascertain the cause of the 

 swelling of the arm after the radical operation 

 for cancer of the breast. This swelling has been 



