394 M. E. Claparede on the Theory of the 



the course of a few months tliis spore becomes developed into a 

 Vaucheria *. 



Pringsheim has also completed the observations of Thuretf 

 and Decaisne on the reproduction of the Fucacese, studying par- 

 ticularly the common Fucus vesiculosus. In this it is not the 

 spores, properly so called, that are fecundated, but these give 

 origin in their interior to eight secondary spores {Theilsporen). 

 During the ebb tide, at the moment when the plants are left 

 dry upon the beach, these secondary spores issue from the 

 mother-spore, and the antheridial sacs also quit the envelopes of 

 the male organs. On the return of the tide, the antheridial sacs 

 burst and give issue to the spermatozoids. These then press in 

 crowds round the secondary spores, w^hich are not yet enveloped 

 by any membrane, and penetrate into their interior. After this 

 fecundation, each secondary spore envelopes itself in a membrane 

 and becomes developed into a Fucus. In this we have a case 

 exactly analogous to that of the animal ovum, in which the 

 spermatozoa penetrate into the vitellus before the formation of 

 the vitelline membrane, or when it no longer exists (as in the 

 Earthworms, according to Meissner). 



In the Floridefe, it appears that there are two kinds of spores, 

 of which some reproduce the plant asexually, whilst the others 

 give rise to a product analogous to the prothallium of Ferns, or 

 the pro-embryo of Mosses. It is upon the latter that fecunda- 

 tion takes place. In the Angiospermeae of Kiitzing, Pringsheim 



* A discovery exactly analogous to that of Pringsheim on the Vaucherice 

 has lately been made by Cohn in a Conferva {Sphceroplea annulina, Ag.). 

 In the cells of this plant stellate spores are produced, which, in their form, 

 })resent a most deceptive resemblance to the reproductive bodies of the 

 Volvox stellatus, Ehr. (hibernating spores of Stein). In the spring, the 

 contents of these spores divide into two, and afterwards into four or eight 

 parts, which become developed into zoospores. These zoospores move 

 about for a certain time in the water, then fix in some place and give rise 

 to young Conferva?. This is a first asexual generation. These young 

 Confervae, in fact, are only a kind of prothallium, for new spores, or rather 

 new sporangia, are formed in their filaments ; these present sexual dif- 

 ferences. Some which present themselves in the form of a membrane, 

 pierced with a certain number of apertures, have contents which become 

 converted into spores ; these are the archegonia. The others, the mem- 

 brane of which is also pierced with several apertures, contain small, 

 mobile, baculiform bodies ; these are the antheridia, with their spermato- 

 zoids. The spermatozoids escape from their prison by jiassing throvigh 

 the apertures of the membrane, and, swimming through the water, go in 

 search of the archegonia, into which they penetrate by passing the aper- 

 tures of their membrane. Cohn has directly observed this interesting 

 pha?nomenon. (Monatsbericht der Berl. Akad., May 1855.) 



t [Thuret had previously seen and described minutely this {)rocess of 

 fecundation : see Proc. Soc. Cherbourg, i. p. 161, and Ann. d. Sc. Nat. 

 4th Ser. ii. p. U*7.— Ed. Ann. Nat. Hist.] 



