The Central Body of the Ascomycetes

R. A. I-Tarper (1905) proved that a apparatus is an essential, integral part of the ascomycetous architecture and that the astral rays emanating from the body initiate a clcavage nrhich cuts the spores out from the cytoplast and leaves the surroullding thein in the ascus. But Harper was careful to say central bodies rather than because, although the apparatus is obviously the source of the astral rays, the cell centers of the Ascomycetes are different from the extremely monomorphic centriole of the cell. Harper described the body in Phyllactinia as a disc pressed upon the surface of the nuclear vacuole, but Dodge (1927) described a hook-shaped body in Nezrros.porn. Berlin and Boxvcn (1964) found the convcntional animal centrioles in the Phpcomycete, Albalgo canididn, but thc Phycomycetes are probably not closely related to the Ascomycetcs. Dodge confirlncd the fact that the astral rays originating from thc apparatus in Nezrrosportr served, as they did in Phyllactinia, to cot out and separate the sporc cytoplasm froin the epiplasm of the ascus. (Harper's insistence on the importancc of this unique process of free-cell and the difference of this type of ccll formation from all other ltnown types of cell formation, or cell-division, has not been accorded sufficient importancc in cell-theory.) Singleton (1953) reexanlined the centriole of N e z a o ~ p o ~ n a d concluded that it resembled an equilaterally triangular disc lvl~ich might loolc likc an ulnbrella handlc in side-view. Singleton's allalysis suggests that thc shape and structure of the centriolc may be the samc in both Phyllactinia and Neurospora. The dimensions of thc centriole in the ascus were 0.5 microns thick and 2.5 microns on the edgc. Since the vegetative iluclcus may bc only about 0.5 nlicroll in dialnetcr while the zygote llucleus in N e z ~ ~ o s p o ~ n is about 20 microns in diametcr, the centriole must vary in size with the sizc of the nuclcus. Such variability xvould stand in inarlted contrast to the rcgularity of size and structure characteristic of thc anillla1 centriole. The rlucleus of the Ascomycetes is unique in another way sillcc the membranc of thc nuclear vacuole never breaks down in the Ascomvcetes. Haruer J 1 inferred that each of the suindle fibers of the intranuclcar suindle lllailltailled a I I perniancnt attachment to the body throucrh a slit in the nuclear vacuole. n. Sinlilar ideas concerning the perillancllt connectloll at thc spindle fibcrs with the cclltriole in aninlals have bcen expressed by Lettri and LettrC (1958). In the Chromone Theory of Mitosis, Lindegren (1962) explains that genetical evidence malces it llllpossiblc to adni t thc pcrlnanent collllection of the body of thc Ascomycetes to the spindle fibcrs. Yuasa and Lindegren (1959) in thc cytological study of yeast by phasc microscopy concluded that thc apparatus in the yeast cell could be identified with a structure extcrnal both to the nuclcar vacuole and to the rigid