29G THE PHENOMENON OF 



7. The conjugation takes place with participation of 

 the entire membrane; inside the double-cell thereby formed 

 the internal membrane contracts into narrower limits, 

 aioay from the wall of the expanded isthmus, forming a 

 cruciform or quadrangular internal cell ; inside the latter 

 the contents contract again to form finally a globular 

 spore This case is required by the preceding as con- 

 clusion of the series. If we have placed Staurocarpus 

 properly under 4, and if it be correct that, as Ralfs* 

 remarks, in passing, in the description of the conjugation 

 of Tetmemorus, there exists a species of Staurocarpus in 

 which a globular spore is formed inside the quadrangular 

 cell by further contraction of the contents, this case does 

 really occur. 



B. Conjugation of dissimilar cells. — I know of 

 no other cases to place in this entire second section, but 

 the conjugation of Vaucheria asserted by Nageli,t which 

 case, however, although I cannot but confirm Nageli's 

 observations, is not yet placed beyond doubt in my 

 mind. A certain reciprocal action of the slender hook- 

 shaped sterile branchlets or horns as they are called 

 (the anthers of Vaucher), and the thick inflated lateral 

 branchlets which produce the spore in the extremity, 

 cannot well be denied. Even Vaucher if described the 

 application of the former upon the latter, and figured it 

 in Vaucheria sessilis ; Hassall§ observed that in those 

 species in which the spore-forming branchlets emerge in 

 considerable numbers from the base of a simple horn, as 

 in Vaucheria geminata, the spore-forming branchlets, 

 vice versa, apply themselves upon the horn, and subse- 

 quently remove again and curve backwards. According 

 to Nageli's and my own observations on Vaucheria 



of the cells of an unconjugated piece oi Desmidinm Swartzii. Might another 

 filament have been connected with this, and again detached after being 

 emptied P 



* L. c, p. 146. 



t See 'AJgensyst.,' p. 175, t. iv., f. 21, 22. 



X 'Hist, des Conferves d'Eau Douce," (1803,) p, 17, t. ii, f. 7 



§ Hassall, 1. c, p. 49, t. 3, f. 1. 



