CIIRONIZOOSPORES OF HYDIIODICTYON. Ill 



the other Draparnaldlce, and which germinate immediately. 

 They present, as do many of the others, the red spot, to 

 which recent observers seem to attribute a great importance. 

 They are produced cither singly, or from two to four to- 

 gether, within each parent-cell, and when the parent is dis- 

 tended and broken up, they usually escape, and move about 

 for some time in the mucilage v. hich envelops the plant ; 

 but they are unable to wander far from their cradle, and at 

 last become motionless, and are transformed into chroni- 

 spores by changing their integument. The modifications of 

 their internal plasma and constitutive membranes, which 

 tliey subsequently exhibit, quickly efface all the distinguish- 

 ing characteristics of zoospores, and give them, on the con- 

 trary, the appearance of the germs Avhich are intended to 

 resist a long suspension of vegetation. 



Usually the transformation of the soft envelop of the zoo- 

 spore into the resisting membrane common to chronispores, 

 takes place only after they have assumed a globular form ; but 

 it often happens that the zoospore continues to move; and it is 

 then under the form that it possesses at that instant that it is 

 consolidated or hardened into a chronispore. Such is the origin 

 of those remarkable bodies that are frequently met Avith among 

 chronispores, and which so closely resemble zoospores. The 

 movement of the zoospores of Draparnaldia glomerata, before 

 their metamorphosis into chronispores, resembles completely 

 in its external character that of other zoospores; the corpuscles 

 of which we are speaking, are, however, less lively, and do 

 not spread themselves so far from the place of their birth, 

 which may, perhaps, be attributed as much to the opposition 

 offered by the mucus which surrounds Draparnaldia, as to 

 their natural inertness, added to the brevity of their active life. 

 From these reasons it happens to them more frequently 

 than to the zoospores of other algee, that they never issue 

 from the parent-cell, but remain in them until all motion has 

 ceased, although the dehiscence of these cells permits them 

 easily to make their escape. This circumstance appears to 

 indicate that the period of agility is of little importance to 

 them, and that an insensible transition takes place between 

 the spores of Drapariialdia and the other reproductive bodies, 

 as much in these algse as in their allies, amongst which I have 

 never observed any sign of movement. 



As regards the spores of the genera Stigodmm and Chceio- 

 phora, their form, which is at first elongated and narrow, 

 recalls that of the zoospores and authorises the belief that a 

 certain time at least, however brief, they have possessed mo- 

 tility. The partitions that separate the parent-cells, appeal" 



