Zoology of Invertebrates By ARTHUR E. SHIPLEY,

Zoology of Invertebrates By ARTHUR E. SHIPLEY,

The simplest forms of Gymnomyxa are grouped together in the class Proteomyxa. As an example of this class the lifehistory of Protomyxa aurantiaca, a minute organism found in 1867 by Professor Haeckel, living on the coiled shells of the Mollusc Spirula, in the Canary Isles, may be described. Many of these shells were found bearing on their white surface a minute globular mass of an orange – l^rown colour. Each globule or cyst consisted of a central mass of protoplasm, surrounded by a structureless membrane ; in the older cysts the central protoplasm appeared to be segmented into a number of parts, each of which, on the bursting of the membrane, escaped in the form of a flagellula or pear-shaped swarm-spore. These moved actively about by the lashing of their whip-like pseudopodium, and soon underwent a change in form ; instead of one pseudopodium which acted as a flagellum, they developed several, and then moved about like so many amoebae. After creeping about for some time, these amoeboid organisms fused together and formed a plasmodium, which in some cases attained such a size as to be visible to the naked eye. The Plasmodium gave rise to many branching ragged pseudopodia, by whose aid it ingested great numbers of diatoms and other food particles. It was much vacuolated, although none of the vacuoles were contractile. After crawling over the Spirula shell for a time the plasmodium retracted its pseudopodia and became spherical ; it then surrounded itself with a cell wall, and the contents of the cyst thus formed broke up into flagellulae in the way indicated above. No nucleus has yet been observed in any phase of the life-history of this organism. Other genera have been described which live parasitically upon Spirogyra ( Vampyrella spirogyrac) or Diatoms (Archerina Boltoni, described by Lankester). In the latter chlorophyll corpuscles are present, and seem to dominate the cell body in a manner suggestive of a nucleus, which is otherwise absent.

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