. The cell in development and inheritance. Cells; Cells. I04 THE GERM-CELLS sory filaments and other structures. At the tip the axial filament may lose its envelope and thus give rise to the so-called " end-piece " (Retzius). In Triton, for '^ - example (Fig. 48, F^, the envelope of the axial fila- ment (" principal filament ") gives attachment to a re- markable fin-like membrane, having a frilled or undulat- ing free margin along which is developed a " marginal ; Towards the tip of the tail, the fin, and finally the entire envelope, disappears, leaving o
. The cell in development and inheritance. Cells; Cells. I04 THE GERM-CELLS sory filaments and other structures. At the tip the axial filament may lose its envelope and thus give rise to the so-called " end-piece " (Retzius). In Triton, for '^ - example (Fig. 48, F^, the envelope of the axial fila- ment (" principal filament ") gives attachment to a re- markable fin-like membrane, having a frilled or undulat- ing free margin along which is developed a " marginal ; Towards the tip of the tail, the fin, and finally the entire envelope, disappears, leaving only the axial filament to form the end-piece. After macera- tion the envelope shows a conspicuous cross-striation, which perhaps indicates a spiral structure such as oc- curs in the mammals. The marginal filament, on the other hand, breaks up into numerous parallel fibrillae, while the axial filament re- mains unaltered (Ballowitz). A fin-membrane has also been observed in some in- sects and fishes, and has been asserted to occur in mammals (man included). Later observers have, how- ever, failed to find the fin in mammals, and their obser- vations indicate that the axial filament is merely sur- rounded by an envelope which sometimes shows traces of the same spiral arrangement as that which is so conspicuous in the connecting-piece. In the skate the tail has two filaments, both composed of parallel fibrillae, connected by a membrane and spirally twisted about each other; a somewhat. Fig. 50. — Spermatozoa of mammals. {A-F from Ballowitz.) A. Badger (living). B. The same after staining. C. Bat ( Vesperugo). D. The same, fiagelhim and middle-piece or connecting-piece, showing end-knobs. E. Head of the spermatozoon of the bat {Rhinolophus) showing details. F. Head of spermatozoon of tliepig. G. Opossum (after staining). H. Double spermatozoa ixova.\!{\ii vas defereiis of the opossum. /. Rat. head-cap (apex) ; k. end-knob (? centrosome); m. middle-piece; n. nucleus (in B, E,
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectcells, bookyear1896
