Handbook of field and general ornithology : a manual of the structure and classification of birds / with instructions for collecting and preserving specimens.

  • Coues, Elliott, 1842-1899.
Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: Handbook of field and general ornithology : a manual of the structure and classification of birds / with instructions for collecting and preserving specimens. Source: Wellcome Collection.

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    placental mammals. No prostate or Cowperian glands exist in birds. The sole office of the testis, or .odjphoi'on masculinum, is the secretion of semen, associate structures being simply accessory for the conveyance of that vital substance and its transference to the opposite sex. The seminal fluid itself is merely the vehicle of transport of the sperma- tozoa, in which their activity may be freely exercised in their intuitive struggles to gain access to their mates in the ovary. It is literally a “ sea of life ” in which the minute creatures swim in shoals to their destiny— and their fate in any case is death. If they successfully bulfet the waves of fate they find a watery grave in the ovum at last; if that „( haven be not reached they simply perish in magnified; from owen, after mid-ocean. I he spermatozoa, or seminal animalcules, or male Dynamamcebm (Figs. 106, 107), are the exact counterparts of ovarian ova, in so far as they are single-celled animals of a very low grade of organisation; but their activity and intelligence are marvellous, and still more so is the mysterious attri- bute with which they are endowed of assimilating their protoplasmic substance with that of the ovum; with the result that the thus fecundated ovum is capable of procreating itself by fission for a period until a mass of similar creatures is engendered; from which mass is then speedily evolved the complex body of the Bird. The corresponding female Dynamamoelce (ovarian ova) are simj^le spherical animalcules, physically indistinguishable from an ordinary encysted Amcela; but the spermatozoa are remarkably distinguished in appearance, furnishing probably the best marked matozoa of^s^?row’ case of sexual characters to be found among the P>'otozoa, to whicli class of aiiimals they belong. The Wagner and Leuck- spermatozoa resemble flagellate infusoria or ciliated endothelium cells, though they each have but a single whip. They are of extremely minute size, much smaller than their females, and filamentous; more or less thickened and some- times wavy at their nucleated heads, whence protrudes an excessively delicate thready tail, endowed with great vibratory energy. They may be likened to diminutive attenuated tadpoles, which swim by lashing the tail in the seminal fluid. Under the microscope shoals of these curious creatures may be seen swimming in the sea, nosing about in search of the ovum, butting their heads in wrong places, backing out and trying again in another direction ; with such success