The micrographic dictionary : a guide to the examination and investigation of the structure and nature of microscopic objects / by J.W. Griffith and Arthur Henfrey.

  • Griffith, J. W. (John William), 1819?-1901.
Date:
1860
Catalogue details

Licence: Public Domain Mark

Credit: The micrographic dictionary : a guide to the examination and investigation of the structure and nature of microscopic objects / by J.W. Griffith and Arthur Henfrey. Source: Wellcome Collection.

    20/773 (page 6)
    distinct. The ordinary strong acid (sp. gr. 1048) should he used. ACHETA.—A genus of Orthopterous in- sects, one species of which, A. domestica, the house-cricket, is familiar to everyone. The general structure of this insect agrees so closely with that of Blatta orientalis, the common cocki’oach or black beetle, which is described at some length, that it requires no special notice here. (See Blatta.) Some parts of the internal structm'e of the cricket are very beautiful, as the tongue (PI. 26. fi. 23) and the gizzard (PI. 27. fig. 1). These, as also the curious mechanism by which the chii-ping noise of the male is pro- duced, are described under Insects. ACHLYA, Nees {Saprolegnia, Kiitzing). —A genus of Siphoneae (Confervoideae). Remarkable microscopic plants, here referred to the Algae, but by some accounted as Fungi. Cienkowski has recently confirmed the idea foi-merly entertained, that Adilya is an aquatic form of the Mucorinous Fungus called Sporeivdonema Mmcce (Empusa Muscce, Cohn), the common fly-fungus. Cohn and Al. Braim deny the identity, while Berkeley thinks Adilya may be an aquatic form of Botrytis Bassiana. They are found mowing parasitically upon the bodies of dead flies lying in water, also upon fish, frogs, &c., and in some cases upon decajdng plants. To the naked eye they appear like colourless minutely filamentous Lifts ad- herent to such objects, forming a kind of gelatinous cloud more or less enveloping them. When placed beneath the microscope, the tufts are seen to consist of long, colour- less, tubular filaments, spreading out in all directions, with or without lateral branches; these erect filaments arise from a kind of my- celium of ramified filaments lying upon the object upon which the plant grows. The erect filaments are devoicl of septa, narrowed upwards, and vary in thickness,heing usually of smallest diameter in those cases where they are closely crowded; the ordinary thick- ness varies from 1-1000 to 1-360 of an inch. The tubes contain a colomless, slightly gra- nular protoplasm, which is denser on the walls, and these sometimes exhibit an irre- gular spiral an’angement of the granules; the granules are seen to move slowly in ana- stomosing currents running in various direc- tions, exhibiting, that is, the well-known pluenomenon of the circulation of cell-con- tents, such as is met with in the hairs of Tra- descantia, &c. The walls of the tubes are coloured blue by iodine and sulpburic acid, therefore consist of cellulose; the contents are nitrogenous, taking a bright yellowish brown with iodine; no trace of starch or of chlorophyll can be detected in the ceU-cou- tents in this stage, whence these plants are regarded by some authors as Fungi; but, as mentioned hereafter, Pringsheim states that their ripe spores do contain starch. Kiitzing describes a number of species of this genus, under the name of Saprolegnia, while a recent observer, Pringsheim, regards them all as forms produced by varying ex- ternal conditions. The latest writer on this subject, A.'de Bary, separates Adilya proli- fer a, Nees, from Saprolegnia ferax, Kiitzing, referring^ to the former the Saprolegnia fe- rax of Carus and the Saprolegnia capituli- fera of Alex. Braun, to the latter the Adilya prolifera of Cams, and, doubtfully, the S. molluscorum of Nees and Gruithuisen. The distinction between these is said to lie in the details of the formation and emission of the active gonidia or zoospores, but we can- not make out satisfactory differences. The following details respecting the for- mation of the active gonidia and the resting spores, are given at length on account of their well illustrating modifications of free- cell formation. In about thirty-six hours after the appearance of a specimen on any body, the apices of the erect filaments exhibit remarkable changes. The granular protoplasm, which at fii-st was equally dif- fused throughout the tube, only densest where it lies on the wall, increases in quan- tity and “ travels up ” into the end of the tube, becoming accumulated there, giving it a brownish colour and at the same time causing its distension, so that the upper part of the tube acquires a clavate form, rounded off above. A shaiqiline of demarcation is soon formed by the division of the primordial utricle, followed by the production of a sep- tum, which shuts off this clavate joint as the sporange; and a little projecting pouch or beak is developed at the summit, or sometimes a little below this on one side. The contents,becoming stiU more condensed, again apply themselves as a thick invest- ment on the wall, leaving a lighter space in the middle of the cavity. Inequalities, or nodular protuberances, are soon observable in this layer, and it speedily becomes broken up into nmiieroiis littie isolated portions, the individualization of these commencing at the summit of the sporange and becoming com- pletedgraduallyfrom^ovedownwards. The end-cell is now a clavate sporange fiUed ivith