A list of ovariole numbers in 329 species in 45 families of Coleoptera is presented of which about one-third are determinations made by the author. The polytrophic Adephaga have a. range of 4–40 ovarioles, the acrotrophic Polyphaga, 1–200 ovarioles, The Coprinae (Scarabaeidae) are the only group containing a single ovary. A few families such as the Curculiomdae contain nearly a uniform number of ovarioles. The work is briefly discussed from the viewpoint of taxonomy, evolution, and fecundity. It is suggested that ovariole numbers may be of aid to taxonomists; that multiplication, reduction, and stabilization of ovariole numbers have occurred in the evolution of beetles; and that extremes in ovariole number may reflect extremes in the level of egg production.
The differentiation of the gonad is described in chum salmon embryos and alevins. Contrary to classical findings in teleosts, sex differentiation in the chum salmon proceeds in the male or female direction without an intermediate female phase. From an initially indifferent gonad there is a progressive development of one sex or the other. The organ forms as a fold from the splanchnic mesoderm and, at the time of first appearance, contains primordial germ cells. These enlarge to form the definitive germ cells which, after a series of divisions, form smaller oogonia or spermatogonia. Oogonia are followed by primary and secondary (growing) oocytes, the appearance of which is the criterion of sex distinction. Spermatogonia continue to multiply but do not undergo growth in the alevin. The ovary develops an open endovarial canal and is supported by a prominent mesovarium. The testis remains small and, in the alevin, develops no ducts. It is suspended by a mesorchium.
Exposure of the arrhenotokous parasite Macrocentrus ancylivorus Rohw. to 23 μg./cm.2 of DDT for 3 minutes in each of 10 successive generations increased the level of resistance to four times that of the original stock. When the concentration of DDT was increased to 96 μg./cm.2 of DDT for 3 minutes from the F11 generation on, the resistance reached a maximum of 12 times that of the initial stock at the F19 generation, and at the F29 generation was nine times the original level. In the F30 to F71 generations, when only females were exposed to DDT, the level of resistance fell to seven times its initial value. When, beginning with the F72 generation, the parasite was reared for 13 generations without exposure to DDT, resistance fell to its initial level. Females were more DDT-resistant than males.
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