. The American Arbacia and other sea urchins. Sea urchins; Arbacia punctulata; Sea urchins -- Embryos; Biology -- Research. THE AMERICAN ARBACIA. Fig. 11. Drawing of Arbacia punctulata spermatozoon. "there is an exceedingly minute opening in the point of the head", through which "one gets the impression that the spermatozoon ehmi- nates very small amounts of an extremely sticky substance". The head of the sperm contains the haploid group of chromosomes which have a volume, if they are the sole components of the sperm head, of about [j,^. A diploid group of 38 chromosome
. The American Arbacia and other sea urchins. Sea urchins; Arbacia punctulata; Sea urchins -- Embryos; Biology -- Research. THE AMERICAN ARBACIA. Fig. 11. Drawing of Arbacia punctulata spermatozoon. "there is an exceedingly minute opening in the point of the head", through which "one gets the impression that the spermatozoon ehmi- nates very small amounts of an extremely sticky substance". The head of the sperm contains the haploid group of chromosomes which have a volume, if they are the sole components of the sperm head, of about [j,^. A diploid group of 38 chromosomes from a first cleavage cell in a smear preparation stained with aceto-carmine has a volume of about [Ji^ (average diameter of a spherical chromosome is about (x), a little more than double that of the sperm head. The expected double relation is fairly close when one considers the uncertainty as to how much of the material is pure chromatin both in the diploid plate of chromosomes and in the haploid sperm head. The amount of DNA in the Arbacia sperm is x io~^ micrograms, calculated as to [x^ according to Mazia (personal communication, 1955), or about one third of the volume (or weight) of the head. Marshak and Marshak (1953) give X io~^ micrograms in one sperm. The middle piece of the spermatozoon of Arbacia punctulata contains two large spheres, probably centrosomes, especially well seen with the phase microscope. These bodies in the middle piece stain purple with methyl green and blue with Janus green, indicating the presence of. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvey, Ethel Browne, b. 1885. Princeton, Princeton University Press
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