No abnormalities during mitosis are seen in mutant ganglion cells. First meiotic spindles are almost normal in ms(1)516¹/Y males. All first division cysts contain 16 cells with four bivalents, indicating that gonial divisions are normal. Second division meiotic spindles are unipolar with respect to astral rays. Chromosomes move to the poles as highly condensed bodies and centromere separation is only rarely seen. Spermatids show variation in nuclear size; macro- and micro-nuclei are readily detected. In about 10% of cases a completely normal cyst with no micronuclei is seen, although normal second division spindles are never seen. Nebenkerne, although defective, are organised and spermatids elongate quantitatively and qualitatively at least as much as in "wild-type" XO males. In the second division meiotic spindles, there are two centrioles at the astral pole, both of which attach to the spermatid nucleus and form tails, but there are no centrioles at the other pole.

Second division spindles are monastral but bipolar in mutant testes. The astral pole is more diffuse than the anastral one, which has an extreme barrel shape. The polar movement of chromosomes is abnormal, mostly to the anastral pole, and the chromosomes move to the poles as dyads without centromere division or separation of the chromatids. The 55-64 spermatid nuclei in the postmeiotic cysts are extremely variable in size and many micronuclei are seen. Cysts with no micronuclei are quite rare - less than 10%. There are pairs of nuclei in the 64-cell cyst; one of which has two centrioles whereas the other has none. In most cases, the two centriolar bodies are attached to the nuclear membrane, although in some cells only one of the centrioles is attached to the nucleus while the other, although still residing in its neighbourhood, is detached. Variable numbers of sperm heads mark the tail end in spermatid bundles.