158 GENERAL HISTOHY OF THE INFUSORIA. 



others with the gonidia abeady distinct (fig. 63), while many parent fronds 

 present the young fronds more or less regularly arranged in the softened 

 and expanded parent mass, which ultimately dissolves and sets them free 

 (fige. 64, 65). They then increase in size in proportion to the favoiu^able 

 conditions in which they are placed. I have never seen anything like what 

 are described by Cohn in Ste_phanos])licera as ' microgonidia.' In a letter re- 

 ceived from Professor A. Braun since the above was written, he speaks of the 

 forms mth small gonidia (fig. 64) as the ' microgonidial ' form. 



''When kept for some weeks, an increasing quantity of fi-onds became 

 accumulated at the bottom of the water, and these chiefly of the character 

 shown in fig. QQ, but devoid of ciha ; and while many of them decayed, in 

 others the gonidia became encysted so as to form globular cellules. Left for 

 a fortnight, the water was found without a trace of green colour, with merely 

 a broA\Tiish sediment at the bottom, upon examining which, it was found to 

 contain a large number of berry-like forms with the gonidia not only en- 

 cysted, but with their contents converted into a red, oily, granular substance 

 (figs. 67, 68), as in the resting- spores of many Confervoids. The gelatinous 

 frond was here almost dissolved away ; and a slight pressure was suificient to 

 detach and separate the cellules, which are doubtless resting-spores (fig. 69) 

 and destined to become subsequently developed into new fronds. This remains 

 to be decided. 



" The organism thus described is a well-marked and distinct species, very 

 diff'erent from Volvox and Gonium, but approaching near to StephanosjphcEra. 

 The form which produces the resting-spores, after losing its ciha, is Kiitzing's 

 Botryocystis Mornm. I have met with a form hke this not imfrequently, but 

 never before with the perfect Pandorlna. Mr. Pollock tells me that he has 

 collected from the same pond for some years past, but never found Pandorina 

 before, and yet it colours the water green this season. VoJvox seems, in Hke 

 manner, to come and go at intervals of years, its revivification from the rest- 

 ing-spores depending much on external conditions." 



Mr. CiuTey's valuable contribution to oiu" knowledge of the British freshwater 

 Algae {J. M. S. 1858, p. 213) furnishes the following memoranda on Pan- 

 donna. He writes — " In speaking of the reproduction of Pandorina, Mr. 

 Henfrey mentions two processes : 1. the conversion of each gonidium into a 

 new frond wdthin the parent mass ; and 2. the conversion of the gonidia into 

 encysted resting-spores, which are set free, and subsequently germinate to 

 produce new fronds. Upon this I may remark, that the process of becoming 

 encysted does not invariably take place ivithin the parent frond, for I have 

 seen the gonidia of Pandorina escape from the parent frond in the form of 

 membraneless active zoospores ; and although I was not fortunate enough to 

 trace the subsequent fate of these zoospores, the probabihty is that, like those 

 of CJdamydococcus and Gonium, they would become encysted at a subsequent 

 period, as, without undergoing this process, it is difficult to see how they could 

 produce new fronds. This mode of escape of the zoospores seems to throw 

 some doubt upon the suggestion of Mr. Henfrey with regard to the nature of 

 the frond of Pandorina, which he considers to be sohd, inasmuch as it does not 

 give way or become indented by pressure, as is the case with the hollow frond 

 of Volvox. If, however, the frond were solid, the zoospores could not well 

 escape, except by its gradual dissolution ; but, in the instance I have men- 

 tioned, the escape certainly took place by a rupture (as may often be seen 

 with Volvox), and not by a gradual process of dissolution. In a paper on 

 some Volvocinece by Dr. Fresenius, in the second volume of the Transactions 

 of the Senckenberg Natural History Society, he speaks of the easy escape of 

 the cells of Gonium pectorah as being evidence against the existence in that 



