252 THE MICROSCOPE AND ITS REVELATIONS. 



are distinguishable by the naked eye as clusters of minute colorless fila- 

 ments; and these are found, when examined by the microscope, to be long^ 

 tubes, devoid of all partitions, extending themselves in various directions. 

 The tubes contain a colorlesss lightly-granular protoplasm, the particles of 

 which are seen to move slowly in streams along the walls, as in Chara, the 

 currents occasionally anastomosing with each other (Fig. 149, c). Within 

 about thirty-six hours after the first appearance of the parasite on any 

 body, the protoplasm begins to accumulate in the dilated ends of the fil- 

 aments, each of which is cut off from the remainder by the formation of 

 a partition; and within this dilated cell the movement of the protoplasm 

 continues for a time to be distinguishable. Very speedily, however, its 

 endoplasm shows the appearance of being broken up into a large number 

 of distinct masses, which are at first in close contact with each other, 

 and with the walls of the cell (Fig. 149, A), but, which gradually become 

 more isolated, each seeming to acquire a proper cell-wall; they then begin 

 to move about within the parent-cell; and, when quite mature, they are 

 set free by the rupture of its wall (B), to go forth and form new attach- 

 ments, and to develop themselves into tubiform cells resembling those 

 from which they sprang. Each of these ' motile gonidia' is possessed of 

 two flagella; their movements are not so powerful as those of the zoo- 

 spores of Vaucheria, and come to an end sooner. The Generative process 

 in this type is performed in a manner that may be regarded as an advance 

 upon ordinary conjugation. The end of one of the long tubiform cells 

 enlarges into a globular dilatation, the cavity of which becomes shut oft 

 by a transverse partition. Its contained endoplasm divides into two, 

 three, or four segments, each of which takes a globular form, and is then 

 fertilized by the penetration of an antheridial tube which comes off from 

 the filament a little below the partition. 1 The ' oospores ' thus produced, 

 escaping from the globular cavities, acquire firm envelopes, and may re- 

 main unchanged for a long time even in water, when no appropriate 

 nidus exists for them; but will quickly germinate if a dead Insect or 

 other suitable object be thrown-in. 



251. One of the most curious forms of this group is the Hydrodiclyon 

 utriculatum, which is found in fresh-water pools in the midland and 

 southern counties of England. Its frond consists of a green open net- 

 work of filaments, acquiring, when full grown, a length of from four to 

 six inches, and composed of a vast number of cylindrical tubular cells, 

 which attain the length of four lines or more, and adhere to each other 

 by their rounded extremities, the points of junction corresponding to the 

 knots or intersections of the network. Each of these cells may form 

 within itself an enormous multitude (from 7,000 to 20,000) of 'swarm- 

 spores,' which, at a certain stage of their development, are observed in 

 active motion in its interior; but of which clusters are afterwards formed 

 by their mutual adhesion, that are set free by the dissolution of their 

 envelopes, each cluster, or ' macro-gonidium,' giving origin to a new 

 plant-net. Besides these bodies, however, certain cells produce from 

 30,000 to 100,000 ' micro-gonidia ' of longer shape, each furnished with 

 four long flagella and a red spot; these escape from the cell in a swarm, 

 move freely in the water for some time, and then come to rest and sink 

 to the bottom, where they remain heaped in green masses. It appears 

 from the observations of Pringsheim, 2 that they become surrounded with 



1 See Prof. Sachs's " Text-book of Botany " (translated by A. W. Bennett), 

 p. 12. 



2 ''Quart. Journ. of Microsc. Science," N.S., Vol. ii. (1862), pp. 54, 104. 



