ZOOSPORES. 



[ 826 ] 



ZOOSPORES. 



the parent cell in the state of Primoedial 

 Utricles, and acquire a cellulose coat 

 subsequently, wheu they cease to move, 

 and settle down to germinate and produce 

 a sti'ucture resembling the parent. In some 

 cases (in Hydrobictyon normally, in many 

 other Coufervoids abnormally) they become 

 encysted ■within the parent cell ; and it ap- 

 pears most probable that the small cysts with 

 dense and often spinulose coats, such as 

 occiu- in Sjnroc/yra (PI. 9. tips. 24, 25) and 

 other genera under certain circumstances, 

 are of similar origin. In the Volvo cine^, 

 zoospore-like bodies form the permanently 

 active individuals of the fomilies. 



True zoospores occur pretty generally 

 throughout the Confervoid Algse, with the 

 exception of Oscillatoriacefe, Nostochaceae, 

 and perhaps Diatomacefe, and are described 

 under the heads of the families or genera. 

 A brief review may be permitted here. The 

 largest form is that produced in the apices 

 of the filaments of Vaucheria (fig. 796) ; 

 it is ciliated all over, and very unlike that 

 of any other genus. In CEdogonium (PI. 9. 

 fig. 7 c, k fig. 811) the zoospores are formed 

 out of the whole contents of a cell, and have 

 a crown of cilia aroimd the transparent 

 'beak.' In other Confervaceee, asClado- 

 pJiora (PI. 9. figs. 1.3 i,c'), Covferra (&gs. 

 10 6, lie); in Chpetophoracefe, as in 

 C7ieetnp/tora (fig. 9), Draparyialdia (fig. 

 180, page 271), Stujeoclonimn (PL 9. fig. 

 .5cc); in Ulvaceae, Viva (PI. 9. figs. 2 6, 

 Zc,d), Enferomorpha (tig. 4 6): in Froto- 

 coccus (PI. 7. fig. 2 6), in Achlya, in Desmi- 



Fig. 811. 



h 



Zoospores of (Edofjonium. a have lost their cilia ; 

 and in 6 germination is more or less advanced. Mag- 

 nified .300 diameters. 



diacefe (PI. 10. fig. ll), &c., as in all other 

 cases, they are formed either singly from 

 the entire contents, or in small or large 

 number by the segmentation of the entire 

 contents, and mostly break out in various 

 ways, as pyriform bodies with tAvo or four 

 cilia on the transparent beak, moving ac- 

 tively for a time, and then germinating to 



produce new plants. They appear usually 

 to be surrounded at the moment of discharge 

 by a delicate common .sac, composed of 

 cellulose, which expands and quickly dis- 

 appears, apparently by solution, setting them 

 free ; in PEDiASTRrii, however, this enve- 

 lope appears to be permanent and to hold the 

 gonidia together in the characteristic group 

 or family (PL 10. fig. 11). In Hydrobic- 

 tyon, as de.scribed under that article, their 

 histoiy is different, though the earlier con- 

 ditions are analogous. It has been found 

 that zoospores of two very different sizes 

 are produced in many Coufervoids: these are 

 called macror/07iidia and mkror/on dia by 

 Braun(see Hydrodictyon) ; and a different 

 function is supposed to be exercised by the 

 latter by some authors, who believe they are 

 fertihzing bodies (like Spermatozoids). 



Zoospores exist in a large proportion of the 

 Algae usually included under the Fucoide^, 

 but which Thuret separates under the name 

 of Phfeosporeae. The Phseosporeae have 

 sporangia containing motile zoospores, bi- 

 ciliated like the spermatozoids of the Mela 

 nosporeae (or Fucoideae). This separates 

 them from the latter. The Phaeosporous 

 families bear organs called Sporaxge.s 

 (usually described in Algological works as 

 spores), from which are discharged zoospores 

 agreeing in all essential respects with those 

 of the Coufervoids, except that the two cilia 

 are often arranged fore and aft, instead of 

 being both in front. Examples of these are 

 de.scribed under Ectocarpus, Myrionema, 

 CrTLERiA, Lamixaria, i.'cc. Zoospores 

 have been discovered in Fungi {Pcrono- 

 spora and Cystoptts) by De Bary, and in 

 Lichens by Famitzin : and if Saprolecjnicp 

 are really aquatic Fungi, their existence is 

 then notorious (PL 27. fig. 27). See Sapro- 

 legnia. 



It remains to direct attention to the di- 

 stinction between Zoospores and Sper- 

 matozoids, which are sometimes confused 

 together. This confusion is rendered more 

 imminent by the manner in which i\\e. forms 

 pass one into another. The essential charac- 

 ter of a zoospore is, that when separated from 

 the parent, it usually becomes encysted and 

 at once developed into a new individual 

 resembling tlie parent. An exception to 

 this occurs in some of the zoospores of 

 (Edogoniuji, which, as the amlrospores, 

 produce special structures in which are de- 

 veloped spermatozoids. And in many cases 

 the zoospores conjugate, before becoming 

 encysted (Conjugation). 



