564 MICROSCOPIC FORMS OF VEGETABLE LIFE THALLOPHYTES 



1^ to 3 inches in height. Munier-Charles l believes that many 

 fossils generally regarded as Foraminifera are in reality the 

 calcareous skeleton of algae belonging or nearly allied to the 

 Siphonacese. 



The microscopist who wishes to study the development of zoo- 

 spores, as well as several other phenomena of this low type of vege- 

 tation, may advantageously have recourse to the little plant termed 

 Achlya prolifera, 2 which grows parasitically upon the bodies of dead 

 flies lying in water. Its tufts are distinguishable by the naked eye 

 as clusters of minute colourless filaments ; and these are found, 



when examined by the 

 microscope, to be long 

 tubes, devoid of all parti- 

 tions, extending them- 

 selves in various direc- 

 tions. The tubes contain 

 a colourless slightly gra- 

 nular protoplasm, the 

 particles of which are 

 seen to move slowly in 

 streams along the walls, 

 as in Okara, the currents 

 occasionally anastomosing 

 with each other (fig. 427, 

 C). Within about thirty- 

 six hours after the first 

 appearance of the parasite 

 on any body, the proto- 



Elasm begins to accumu- 

 ite in the dilated ends 

 of the filaments, each of 

 which is then 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 distinguish - 



FIG. 427. Development of Achlya prolifera : A, 

 dilated extremity of a filament &, separated 

 from the rest by a partition a, and containing 

 zoospores in progress of formation ; B, end of 

 filament after the cell-wall has burst, and 

 setting free zoospores, a, b, c ; C, portion of 

 filament, showing the course of the circulation 



of granular protoplasm. 



able. Very speedily, how- 

 ever, 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 arid 

 with the walls of the cell (fig. 427, 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 



1 Comptes Bendus, vol. Ixxx. 1877, p. 814. 



2 [This plant, though, as an inhabitant of water, formerly ranked among Alga;, is 

 now generally regarded as belonging to the group of Fungi, on account of its 

 incapacity for the production of chlorophyll, and its parasitism on the bodies of 

 animals, from whose juices its cells seem to draw their nourishment. It is very 

 closely allied to Saprolegnia (see p. 640), a fungus parasitic on the bodies of living 

 fish, and causing the very destructive disease to which salmon are liable. ED.] 



