SUMMARYCytophotometric methods have been used to demonstrate a fall in the acetic‐alcohol fixable RNA of the cytoplasm of the meiocytes ofCosmos bipinnatusduring the meiotic prophase. The decline occurs between zygotene and pachytene, and is probably attributable to a reduction in the ribosome population comparable with that already known to occur inLiliumandTrillium. Cytoplasmic acid phosphatase activity, estimated by cytochemical methods using naphthyl phosphates as substrates, rises from a low value in the preleptotene period to a maximum in zygotene and then subsequently declines. The possibility is suggested that the change in naphthyl cytochemically detectable acid phosphatase may be connected with the “autodigestive” processes concerned in ribosome elimin