TERMOPSIS ANGUSTICOLLIS. 5 



early and late metaphase, respectively, and figures 29, 30, and 31 in 

 anaphase. This is certainly a reduction division, for the tetrads are 

 always somewhat elongated and come into the spindle with their longer 

 axes parallel with the axis of the spindle. The aberrant bodies in 

 these figures are probably remains of the nucleoli ; they are found only 

 in iron-hsematoxylin preparations. Figures 31 and 32 show excep- 

 tional cases where the cell has divided. Usually the two daughter 

 nuclei are formed in an undivided cell. The resting-stage between 

 the two divisions is only partial. The nucleolus appears and divides 

 into two (figs. 33-36), and the chromosomes change into the dyad 

 form (fig. 36), in which they come into the second maturation spindle 

 (figs. 37, 38). The equatorial plate again shows 26 chromosomes (fig. 

 39) , The formation of the sperlnatozoa is peculiar in that the original 

 spermatocyte cell-body, as a rule, does not divide ; but the four nuclei 

 resulting from the two maturation divisions develop into sperm-heads 

 in one cell. All have a nucleolus (fig. 41), and in a slightly later stage 

 (fig. 42) the elongated nuclei have a distinct centrosome and sphere at 

 the posterior end. Later stages are shown in figures 43, 44, and 45. 



The points of greatest interest in the spermatogenesis of Termopsis 

 angusticollis are, (i) the fact that no accessory chromosome is present ; 

 (2) that the method of tetrad formation and reduction are clear, despite 

 the fact that the cells and the chromatin elements are quite small ; 

 and (3) the failure of the cell-bodies to divide and the consequent 

 development of four spermatozoa in one cell. 



Stenopelmatus. 



The spermatogonium of Stenopelmatus contains from one to three 

 large nucleoli, which stain much less with thionin than does the 

 spireme (plate 11, figs. 46,47, 48). As the distinct chromosomes come 

 into view in the prophase of mitosis, two are seen to be nearly twice 

 as long as the others, but of equal length (figs. 48, 49, 50.) There 

 are 46 chromosomes in the equatorial plate of a spermatogonial spindle 

 (fig 50). Besides the nucleolus (w), there appears in the young sperm- 

 atocyte a conspicuous element {x) which stains deeply with all chro- 

 matin stains (fig. 51). It is closely applied to the nuclear membrane 

 and is connected with an end of the spireme (figs. 51-54). At first it 

 is quite small, and it gradually increases in size during the spireme 

 stage. There is no " bouquet stage " in this form. Figure 55 shows 

 the spireme segmented and split longitudinally. The segments have 

 begun to open out at the center to give the cross which is the typical 

 tetrad form in Stenopelmatus. Figures 56, 58, 59, and 60 show various 

 stages in the contraction of the split segments to form crosses and 



