The Acrididæ are characterised by a very uniform karyotype. With a few exceptions, the species so far studied contain 23 chromosomes in the male, which are very similar in size and structure. Attempts to deduce the probable mechanism of speciation within the Acrididæ were restricted only to metrical studies of chromosomes. Recently, however, Coleman (1943) has established in two species the subterminal position of the primary constriction or centromere and the variation in the length of the two arms in different chromosomes of the same karyotype. In the present paper additional evidence is presented which shows a linear differentiation of some chromosomes of the Acrididæ. Furthermore, in view of the fact that chromosome behaviour during meiosis is a more reliable criterion of ascertaining linear differentiation, the meiosis was studied in three genera.
Three species belonging to three different genera were studied. They are Spathosternum prasiniferum Walker, Oxya sp. and Phlœoba sp. The former two belong to the sub-family Catantopinæ and the latter one to Acrididæ. Adult male specimens have been captured from the field adjoining the Biological Departments, Calcutta University, mostly in the months of August and September 1943–44. The testes were dissected out in Ringer's solution (cold-blooded formula) and fixed in Medium Flemming, Belling's, and Kahle's fixatives. The two latter were very suitable for smear preparations. Sections were cut at 25 to 30 micra in thickness and stained in iodine-crystal violet and in Heidenhain's hæmatoxylin. A 2 per cent, solution of safranin also gave good results. Squash preparations were stained by Feulgen's method. Diplotene stages in Phlœoba were studied from temporary aceto-carmine preparations.