. Evenings at the microscope : or, Researches among the minuter organs and forms of animal life . Zoology; Microscopy; Microscopes. MOUTH OF BRACHIONU8. and the rami of the incus -with the maxillae; while the walls of the mastax with the two edges of its orifice correspond with the mouth, with its labrum and labium. It is true we are somewhat startled to find a mouth placed far down within the cavity of the breast ; but there are other forms in this class, some of which I may be able to show you, where the mastax has es- sentially the same structure, in/ which it is placed at t
. Evenings at the microscope : or, Researches among the minuter organs and forms of animal life . Zoology; Microscopy; Microscopes. MOUTH OF BRACHIONU8. and the rami of the incus -with the maxillae; while the walls of the mastax with the two edges of its orifice correspond with the mouth, with its labrum and labium. It is true we are somewhat startled to find a mouth placed far down within the cavity of the breast ; but there are other forms in this class, some of which I may be able to show you, where the mastax has es- sentially the same structure, in/ which it is placed at the front" margin of the body, from which the jaws can be freely protruded. The difficulty will seem less if you weigh the following considerations:— The integument in the Rotifera is very flexible, and, especially in the frontal regions, is extremely invertible. In those genera in which the mouth apparatus can be brought into contact with the external water, it is ordi- narily, to a greater or less degree, retracted within the body, by the inversion of the surrounding parts of the exterior, while, in those genera in which it is permanently inclosed, analogy requires us to consider the condition as induced by a similar inversion, but of permanent duration. If we imagine the head of a soft-bodied Insect-larva re- tracted to a great degree (as is done partially by many Dipterous larvae), the skin of the thoracic segments would meet together in front, around a purse-like opening, which would be the orifice of such a buccal funnel as exists in most Rotifera. In the latter, it is the normal, or proper, condition; in the former, it is merely accidental and temporary. We need not devote any more minute consideration to the digestive apparatus in our little Brachion, but there. 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
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