Journal of experimental zoology . .6^, giving a ratio of : This is con-siderably less than the ratio : or : , that wouldbe expected for Anax Junius. {d) Conclusion. The presence of two size groups is indicatedby the measurements. 11. Rana pipiens (a) Spermatogenesis evidence concerning dimorphism. Whilea number of investigators have studied the spermatogenesis ofthe frog no chromosomal differences have so far been made outbetween two groups of spermatids. (b) Material and method. Material obtained August 24, 1913,at Douglas Lake, Michigan; motile; killed in osmic
Journal of experimental zoology . .6^, giving a ratio of : This is con-siderably less than the ratio : or : , that wouldbe expected for Anax Junius. {d) Conclusion. The presence of two size groups is indicatedby the measurements. 11. Rana pipiens (a) Spermatogenesis evidence concerning dimorphism. Whilea number of investigators have studied the spermatogenesis ofthe frog no chromosomal differences have so far been made outbetween two groups of spermatids. (b) Material and method. Material obtained August 24, 1913,at Douglas Lake, Michigan; motile; killed in osmic fumes; dia-gram of sperm-head in figure 101; measurements are to tenthsof a micrometer division, one division being equal to (c) Data. Figure 37 gives the frequency distribution of 494spermatozoa from a left testis. Each group covers three-tenthsof a micrometer division. The distribution is bimodal with thesmaller individuals less abundant than the larger. The modesare at ^ and , giving a ratio of : ?«*iO»r5W5»r5»Oif3io»0 Fig. 3G Aeshna canadensis; frequency distribution of head-lengths of 49Gspermatozoa from the right testis. Value in 42 9 44 48 50 53 44 23 54 1 15 7 4 2 3 1 30 33 20
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1904
