SOME UNUSUAL CYTOLOGICAL PHENOMENA IN THE SPERMATOGENESIS OF A HAPLOID PARTHENOGENETIC HYMENOPTERAN, ÆNOPLEX SMITHII (PACKARD)

¹ DEPARTMENT OF ZOÖLOGY, NORTHWESTERN UNIVERSITY

The number of chromosomes as demonstrated by the cytological study of gonial cells is thirteen in the male and twenty-six in the female. Experimentally it was found that virgin females gave rise only to males. In view of the experimental and cytological evidence it is concluded that males having the haploid chromosome number develop from unfertilized eggs and are thus produced parthenogenetically.

The pinching off of a non-nucleated cytoplasmic bud characterizes the first meiotic division.

A monopolar spindle is regularly formed simultaneously with the pinching off of the first spermatocyte bud. This spindle would appear to be of chromatin origin.

The chromosomes or chromosomal masses, with spindle fibers trailing, exhibit pronounced anaphasic movement identified with the first spermatocyte division. The force responsible for this anaphasic movement apparently is entirely independent of the half spindle fibers.

There is no formation of a nuclear membrane between the first and second spermatocyte divisions. However, after their characteristic anaphasic movement the chromosomes gather into a compact mass for an abbreviated interkinesis.

The tendency for the half spindle components to be dragged about by the chromosomes during the anaphase of the first spermatocyte division and during the movement of the chromosomes in the formation of the interkinetic mass would seem to indicate that half spindle fibers have morphological reality.

The bipolar spindle identified with the second spermatocyte division appears to originate as an outgrowth from the interkinetic chromosomal mass. This would seem to be evidence for morphological reality of the fibers.

The second spermatocyte division may be equal, producing two normal spermatids.

Not infrequently aberrant spermatids are formed as a result of the secondary fusing of the parts of a partially divided second spermatocyte. They have a single large nucleus which is formed as a result of the fusion of two normal nuclei.

In early spermiogenesis the development of the two types of spermatids appear to be similar except for differences in size.

At present no evidence is available to indicate that the aberrant spermatids develop into functional spermatozoa.