308 THE PHENOMENON OF 



development recommences. In the Mosses and Terns it 

 is the central cell of the archegonium,* (a sproutlet which 

 may be compared with the nucleus of the ovule,) which 

 is impregnated, in a manner not yet accurately known, 

 through the spermatozoids formed in the antheridia; 

 the development of this, however, is not a recom- 

 mencement of the entire cycle, but only an advance to a 

 new and higher stage of the metamorphosis, which, 

 unfolding in connection with the pre-existing preparatory 

 structure, carries over the individual life only after more 

 or less complex intermediate stages of formation, to the 

 production of the true reproductive cells (spores), with 

 which, and without further impregnation, the new cycle 

 of development commences. The point of transition 

 marked by the occurrence of impregnation, is, again, 

 different in the Terns and Mosses. In the Mosses, the 

 transition from the Algoid prothallium to the leaf-forming 

 stem takes place before the impregnation, which causes 

 only the development of the spore-forming capsule ; in 

 the Ferns, on the contrary, the preparatory structure 

 does not go beyond the leafless prothallium, and the 

 advance to the leaf-forming stem depends upon the im- 

 pregnation. This mode of viewing the case, very strange 

 as the introduction of the impregnation into the midst of 

 the cycle of the individual development may be, appears 

 to me more in accordance with nature, to interrupt less 

 the natural connection, and to correspond better with the 

 graduated course of the metamorphosis, than that given 

 by the discoverer of the archegonia of the Ferns, f 

 according to which the thalloid product of germination of 

 the spore of the Ferns is compared, as the bearer of the 

 impregnation organs, to the flower of the Phanerogamia, 

 while the spore from which it is developed is termed a 



* See Gottsche, on the ' Fructification of the Jungerraannise geocalyceee,' 

 'Nov. Act.,' xxi, ii, 445, t. 30, f. 8. The bicellular condition of the endo- 

 gonium of Calypogeia Tricfiomancs there represented is certainly preceded by 

 a unicellular stage. 



f Leszczyc-Suminski, ' Zur Entwickl. der Farrnkrauter,' Berlin, 1848. 



