276 M. N. rringslR'ini on the Pairing of Zoospores. 



knowledge of the mode of conversion of the niicrogonidia into 

 resting-spores in the Cha'tophorav, and especially in Drapar- 

 7ialdia, will disclose the peculiar bond of union between these 

 two divisions of the Algai. 



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

 copulation in the Zjigosporccv^ it is still more closely allied, on 

 the other hand, with the kno^^^l sexual process in the Zoo- 

 sjwrcte. 



Comparing the sexual act in Pandorina and (Edoijoniumj 

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

 brood-sphere of CEdogoniuni, in front of Avhich, 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 of P«;ifZor«'«a, and with the so-called 

 "mouth" of the directly germinating zoospores of CEdogoniinn. 

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

 spheres of CEdogonium, as well as those of Vaucheria and 

 ColeochcEte, to which those of other Algaj which have a less 

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

 only miciliatcd resting-forms of zoospores. 



But the analogy of the structm-e of the brood-sphere and 

 the zoospore may be extended far beyond the Alg?e. 



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

 which in the embryonic vesicle of the Pha^nogams has been 

 called by Schacht the filamentary process {Faden-App>arat *) 

 is an analogue of the colourless " locus of impregnation " 

 {Befriichtungstelk) in the brood-spheres of Alga3, and of the 

 mouth or germ-s])ot of the zoospores. The canal-cell observed 

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

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

 corresponding organ. The word "germ-spot" {Keimflech) 

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

 tion of female plants in general, which tenn Avould 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 genninal vesicle in Crocus Wahonia and some other 

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

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

 delicate cellulose threads radiating downwards. Schacht's observ'ations 

 have been question-d by Hofraeister, but were partly confirmed by the 

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

 impregnation of frladiolus segetiim (Bot. Zeitung, Jan. 15, 1858^, on the 

 impregnation of Crocus vemus (Regensb. Flora, Sept. 21, 18o8), and on 

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

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

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

 and to Profe.ssor Ht-nfrey's paper on "the Development of the Ovule of 

 Sdutiihim (dhum," in Trans. Linn. Sue. vol. i.xii. — Tu.] 



