Zoology : an elementary text-book / [Sir A.E. Shipley].

  • Arthur Shipley
Date:
1920
Catalogue details

Licence: Public Domain Mark

Credit: Zoology : an elementary text-book / [Sir A.E. Shipley]. Source: Wellcome Collection.

    52/780 (page 28)
    networks are much coarser than in the case of the Thalamophora. The fluid endoplasm is seen to have a regular flow alternately backwards and forwards in these pseudopodia; the movement of the whole mass in any direction being due to the predominance of the forward flow over the backward, or vice versa. When stained the protoplasm is seen to include thousands of very small nuclei. The name Mycetozoa literally means Fungus animals (from Gr. ixvkt]<s) a fungus, £wa, animals). They are also often called Myxomycetes— literally Slime-Fungi, both names having been suggested because their special mode of reproduction leads some naturalists to con¬ sider them to be plants. Their power of encystment is very marked, for the slightest tendency to drought calls it into action, and then a mass will break up into numerous cysts, which will remain perfectly passive until wetted. Before reproduction, the same process occurs, but the nuclei multiply by division and then fuse in pairs with one another; the contents of the cyst then become aggregated round these final nuclei as rounded germs called spores—which acquire walls of cellulose, a constant product of plant life. Such spores are called chlamydospores. In one group of the Mycetozoa known asEndosporeae a portion of the plasmodium swells up so as to form a rounded mass on a stalk which is termed the sporangium and which encysts itself. In another group lobe-like fingers grow out from the plasmodium, from the apices of which spores are constricted off one by one. These are called the Exosporeae. Some of the protoplasm not used in the formation of spores forms long threads of cellulose, called collectively a capillitium, which when wetted expands and so expels the spores. The appearance of cellulose was the only justification for regarding these animals as in any way allied to plants, and it is known that cellulose is quite a constant product in some groups of animals. The contents of the spore escape as a germ propelling itself by a flagellum (B and C, Fig. 7), the germ itself being termed a flag el lu la. This thread is soon withdrawn and the germ takes on the form of a small Amoeba and is then called an amoebula (D, E, and F, Fig. 7). Many of these amoebulae coalesce to form the adult form, which is called the plasmodium (G, Fig. 7), a name given to the result of the fusion of a number of originally separate animals. The Sun animalcules, or Heliozoa (Gr. r/Mo?, the sun), which inhabit, with few exceptions, fresh water, were formerly Heliozoa. . / confounded with the Radiolaria, but they are in reality very different from these. They are spherical in shape and