108 MR. C. F. U. MEEK ON THE CORRELATION OF 



transition to a greater thread-width : it is, however, impossible to prove this- 

 phylogenetic cycle with the meagre data at present available. I£ it is 

 eventually established, we must realize that an attempt to correlate somatic 

 characters and individual chromosomes must fail the moment that we consider 

 any but the most closely allied organisms : at definite periods a complete 

 rearrangement o£ units has occurred, and, since the subsequent rate of growth 

 must have varied in different chromosomes under different conditions of 

 environment, we have no reason for assuming correspondence between rods 

 of the same length found in the germ-cells of widely separated organisms.. 

 Within the limits of a genus, however, it may be possible to trace somatic 

 differences to differences in chromatin growth, for closely allied animals must 

 have developed alonfr the same or parallel lines, and we may therefore be able 

 to identify corresponding chromosomes in their respective complexes. In the 

 paper already referred to I have given camera lucida drawings of chromosome 

 rods composing the complexes of several species of Sfenohofhrvs, and have- 

 shown that the latter can be individually distinguished by the presence or 

 absence of certain rod-lengths ; I now propose to deal with another species- 

 of this genus in order to show that this phenomenon is probably connnon to 

 all its members. Moreover, the comparative study of allied species may 

 enable us to establish some correlation with respect to length of chromosomes- 

 and somatic characters. 



Material and Methods. 



Stenobotlims cirrtipennis, which belongs to the ii'ibe Tryxalidre and the 

 family Acridiida?, is not found in the British Isles, and I am indebted for 

 the material to the kindness of Prof. H. S. Davis, who sent me testes fixed in 

 Hermann's solution and embedded in paraffin, from the University of Florida, 

 Gainesville, U.S.A. The sections Avere cut <S fi thick and stained with 

 Heidenhain^s iron hjx?matoxy]in, the mordant used being an aqueous solution 

 of iron alum. The preparations were studied by means of a Zeiss apochro- 

 raalic oil-immersion objective of 2 nnn. focus and N.A. 1'30, in conjunction 

 with compensating oculars nos. G, 12, and 18 : I have used throughout the 

 holoscopic oil-immersion substage condenser made by Messrs. Watson, o£ 

 High Holborn, London. 



All drawings were made with the aid of a large Abbe camera lucida at a 

 magnification of three thousand and forty-eight diameters, the magnification 

 being estimated by means of a stage-micrometer graduated to read one- 

 hundredth of a millimetre. When necessary, resolution was facilitated by 

 interposing a Griff ord screen. 



In order to avoid error due to foreshortenino;, drawings have been made 

 only of chromosomes that lay at right angles to the microscopic fine of vision 



