I had no intention of making an extended study of the spermatogenesis of the Lepidoptera, but was interested to see if anything corresponding to the heterochromosomes of other orders could be found. The material studied was the testes of the larvæ of _Cacoecia cerasivorana_ and _Euvanessa antiopa_. The number of chromosomes is large, but the equatorial plates are diagrammatically clear. In both species 30 chromosomes are found in both first and second spermatocytes. In both, one chromosome is larger (figs. 290 and 293, _x_). In the growth stage (figs. 283, 284) there is a two-lobed body (or sometimes two separate spherical bodies) which seems to correspond in size to the larger pair of chromosomes in the first spermatocyte. In iron-hæmatoxylin preparations this pair is often obscured by parts of the spireme which are tangled around it. In safranin-gentian preparations it stains, not like a plasmosome, but red like the heterochromosomes, while the spireme is violet. The staining reaction at least suggests that this equal pair of chromosomes, which may be traced through the synizesis stage (fig. 280), synapsis stage (figs. 281, 282), growth stages (figs. 283, 284), and prophases (figs. 285-287), into the first spermatocyte spindle (figs. 288, 290), and on to the second spermatocyte (figs. 289, 291, 292), is an equal pair of heterochromosomes comparable to the equal pair of "idiochromosomes" found by Wilson in _Nezara_ ('05). As the various stages are practically the same in _Euvanessa antiopa_, but somewhat clearer in _Cacoecia_, only one figure is given for _Euvanessa_--the equatorial plate of the first spermatocyte (fig. 293). SUMMARY OF RESULTS. (1) An unequal pair of heterochromosomes has been found by the author in 19 species of Coleoptera belonging to 8 families: FAMILY. SPECIES. I. Buprestidæ Two spruce-borers, species not determined. { 1. _Chlænius æstivus._ II. Carabidæ { 2. _Chlænius pennsylvanicus._ { 3. _Galerita bicolor._ { 1. _Blepharida rhois._ { 2. _Chelymorpha argus._ { 3. _Coptocycla aurichalcea._ III. Chrysomelidæ { 4. _Coptocycla guttata._ { 5. _Doryphora decemlineata._ { 6. _Odontota dorsalis._ { 7. _Trirhabda virgata._ { 8. _Trirhabda canadense._ IV. Cicindelidæ _Cicindela primeriana._ V. Coccinellidæ { _Adalia bipunctata._ { _Epilachna borealis._ VI. Scarabæidæ _Euphoria inda._ VII. Silphidæ _Silpha americana._ VIII. Tenebrionidæ _Tenebrio molitor._ (2) An odd chromosome, which behaves during the growth stage of the first spermatocytes like the "accessory" of the Orthoptera, has been found in 4 species of Coleoptera,[A] belonging to 3 families: FAMILY. SPECIES. I. Carabidæ _Anomoglossus emarginatus._