276 M. N. Pringslieim on the Pairing of Zoospores. 



knowledge of the mode of conversion of the microgonidia into 

 resting-spores in the Ghcetojphorece^ and especially in Drapar- 

 naldia^ will disclose the peculiar bond of union between these 

 two divisions of the Algse. 



Whilst this pairing is connected, on the one hand, with the 

 copulation in the Zygosporece, it is still more closely allied, on 

 the other hand, with the known sexual process in the Zoo- 

 sporece. 



Comparing the sexual act in Pandorina and (Edogonium, 

 we find that the anterior, coloui'less, protoplasmic mass of the 

 brood-sphere of (Edogoiiimn, in front of which, as in Pando- 

 rina, the coalescence with the spermatozoid takes place, is 

 identical with the so-called " mouth " [Mund-Stelle) of one of 

 the two pairing zoospores (A Pandorina, and with the so-called 

 "mouth" of the directly germinating zoospores of (Edogonimn. 

 It may be taken to be undeniable that the resting brood- 

 spheres of CEdogonium, as well as those of VaucJieria and 

 Coleochcete, to which those of other Algffi which liavc a less 

 defined or hardly perceptible germ-spot ai-e closely allied, are 

 only unciliated resting-forms of zoospores. 



But the analogy of the structure of the brood-sphere and 

 the zoospore may be extended far beyond the Algte. 



It would seem to be a result of the foregoing that that 

 which in the embryonic vesicle of the Pha3nogams has been 

 called by Schacht the filamentary process [Faden-Apparat *) 

 is an analogue of the colomdess " locus of impregnation " 

 [Befruchtungstelle) in the brood-spheres of Algte, and of the 

 mouth or germ-spot of the zoospores. The canal-cell observed 

 in the central cell of the archegonium of Salvinia, and Avhich 

 seems to occur also universally in mosses and ferns, is a 

 corresponding organ. The word " germ-spot " (A^eiwi^^cA;) 

 would be a convenient word to express the locus of impregna- 

 tion of female plants in general, which term would include 

 the " mouth " of the zoospores, the colourless protoplasmic 



* [" Fadeii-Apparat " is the term used by Schacht to describe the ante- 

 rior portion of the germinal vesicle in Crocus Watsonia and some other 

 plants. He imagines that it exists in all plants in which the pollen-tube 

 does not penetrate the embryo-sac, and he describes it as consisting of 

 delicate cellulose threads radiating downwards. Schacht's observations 

 have been questioned by Hofraeister, but were partly confirmed by the 

 late Professor Ilenfrey. The reader may refer to Schacht's papers on the 

 impregnation of Gladiolus segetitm (Bot. Zeitung, Jan. 15, 1858), on the 

 impregnation of Crocus vermis (Regensb. Flora, Sept. 21, 1858), and on 

 the impregnation of Santahim album (Pringsheim's * Jahrbiicher fiir wiss. 

 Bot. vol. iv. p. 1), also to Hofmeister's remarks in the 'Bonplandia' for 

 1856, p. 287, and in Pringsheim's 'Jahrbiicher fiir wiss. Bot.' vol. i. p. 162, 

 and to Professor Henfrey's paper on "the Development of the Ovule of 

 Sfiiifdhiiii fdhum," in Trans. Linn. Soc. vol. ixii. — Tr.] 



