The Effect of Radium Radiations on the Development of Chætopterus

Artificial Parthenogenesis

“…In the multiplication of the cytasters and cleavage of the non-nucleated fragment Harvey (1940~) observes no spindle formation. This accords with the generally accepted view that the chromosomes are involved in the formation of the spindle fibres, as is well illustrated, for example, in Packard's (1918) observations showing the absence of spindle fibres to X-rayed chromosomes in C&topterus.…”

“…Similar experiments were performed on salamanders (0. Hertwig, 1913), fish (P. Hertwig, 1916; Oppermann, 1913), seaurchins (G. Hertwig, 1912) and on annelids (Packard, 1914(Packard, , 1918. Exposure of frog sperm to ultra-violet radiation, X-rays or trypaflavin (Dalcq, 1931 ;Dalcq & Simon, 1931 ;Rugh, 1939) has been shown to give similar results.…”

The Effects of X-Irradiation on the Fertilized Eggs of the Annelid, Chaetopterus

“…The occurrence of cleavage retardation reported here is in accordance with the results obtained by other workers. Thus, Packard (1918) observed delays in the division of Chaetopterus eggs irradiated with gamma rays from radium. Cook (1939) demonstrated a two-to five-hour delay in the first cleavage of Ascaris eggs x-irradiated at the one-cell stage.…”

“…There have been many reports in the literature of chromosome aberrations which occur after irradiation from various sources. An early one was the paper by Packard (1918) ; he irradiated unfertilized Chaetopterus eggs with gamma rays from a radium source and observed multipolar spindles at the first cleavage, after the treated eggs had been inseminated. Packard interpreted these multipolar spindles as being due to polyspermy, which he felt was facilitated in some way by the irradiation.…”

Genetic Control of Insect Populations

“…When McClintock described the breakage-fusion-bridge cycle in maize (12), a genetic mechanism was perceived for the origin of the numerous chromosomal bridges and concurrent death of embryos that had been observed previously by cytologists (13) after irradiation of eggs from marine environments. McClintock's observation led to the concept that bridges could cause loss of chromosomes during mitosis, and that loss of chromosomes could cause death because of genic imbalance.…”