SUMMARY OF RESULTS. 49 



SUMMARY OF RESULTS. 



(i) An unequal pair of heterochromosomes has been found by the 

 author in 19 species of Coleoptera belonging to 8 families : 



Family. Species. 



I. Buprestidae Two spruce-borers, species not determined. 



( 1. Chlcenius cestivus. 



II. Carabidae -\ 2. Chlcenius pennsylvanicus. 



( 3. Galerita bicolor. 

 f 1. Blepharida rhois. 



2. Chelymorpha argus. 

 I 3. Coptocycla aurichalcea. 



III. Chrysomelidse \ *' Coptocycla guttata 



J 5. Doryphora decemlmeata. 



6. Odontota dor salts. 



7. Trirhabda virgata. 



I 8. Trirhabda canadense. 



IV. Cicindelidas Cicindela primer ia rice. 



V. Coccinellidae f Adalzab&unctata. 



(. hpilachtia boreatis. 



VI. Scarabseidae Euphoria inda. 



VII. Silphidae Silpha americana. 



VIII. Tenebrionidas 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,* belonging to 3 families: 



Family. Species. 



I. Carabidae Anomoglossus emarginatus. 



II. Elateridae Two Elaters ; species not determined. 



III. Lampyridas EUychnia corrusca. 



(3) In most of the species of Coleoptera examined, the unequal pair 

 or the odd chromosome remains condensed during the growth period 

 of the first spermatocyte, like the " accessory " of the Orthoptera and 

 the various heterochromosomes of the Hemiptera. 



(4) Several of these species of Coleoptera have a synizesis stage in 

 which the spermatogonial number of short loops is massed at one side 

 of the nucleus. This is followed by a synapsis stage in which the 

 loops straighten and unite in pairs, forming longer loops which soon 



*Aug. 20, 1906. — Since this paper was prepared, 19 other species of Coleoptera 

 have been studied. Of these, 17 have an unequal pair of heterochromosomes in the 

 spermatocytes. Six belong to the Chrysomelidas, making 14 of that family that have 

 been examined. Representatives of 4 new families — Melandryidae, Lamiinae, Mel- 

 oidae, Cerambycinse — have been studied. In only two species, — 1 Elater and 1 

 Lampyrid — has the odd chromosome been found in place of the unequal pair. No 

 species of Coleoptera has yet been examined in which one or the other of these two 

 types of heterochromosomes does not occur in the spermatocytes. Of the 42 species 

 of Coleoptera whose germ cells have been studied, 85.7 per cent are characterized by 

 the presence of an unequal pair of heterochromosomes in the male germ cells, 14.3 

 per cent by the presence of an odd chromosome. 



