74 THE NATURAL HISTOET EETIEW, 



any inyesting membrane. There is also in Sphceroplea, the very- 

 remarkable fact, that whilst in Fucus, tbe unimpregnated spores are 

 dispersed over the surface of their thallus where the spermatozoa 

 must come in contact with them, and whilst in Vaucheria the orifice 

 of the antheridium almost joins that of the sporangium, the 

 Sphceroplea have to search out a female cellule, sufficiently developed, 

 and often at a distance, and have then to effect an entrance through 

 narrow apertures designed for the purpose. What the force may 

 be which guides them to their destination. Dr. Cohn pronounces to be 

 a veritable physiological enigma. 



In GEclogonium and Bulhoclicete^^ impregnation is also effected by 

 the action of spermatozoa upon the contents of the female cells or 

 sporangia. The contents of these female cells {Oogonia of Pring- 

 sheim) shortly before impregnation part from the wall of the cell 

 and become contracted into a globular mass, called by Pringsheitn 

 the ^^ BefriLchtungsJcuf/el,'" which is a membraneless rudimentary 

 S]3ore. An opening is formed in the wall of the oogonium, and the 

 nature of this opening as well as the form of the rudimentary spore 

 varies in different species. The simplest and most frequent opening 

 is by a small oval hole in the membrane of the oogonium, formed at 

 the same time as the rudimentary spore. The portion of the latter 

 which adjoins the opening is covered with a colourless protoplasm, 

 which projects as a papilla. The spermatozoon touches and becomes 

 intermixed with the pai)illa, which then retracts itself into the 

 oogonium and the impregnation of the spore is effected. 



The most remarkable point in the impregnation of the CEdogenieso 

 is the different mode in which the spermatozoa originate in different 

 species. In some species of (Edogonium they are produced directly 

 from certain cells which are true antheridia — the antheridia and 

 oogonia occurring in most cases upon separate plants, but in some 

 instances upon the same plants. This is quite similar to what occurs 

 in other Algas. But in other species of (Edogonium, and in most, if 

 not all, of Bidhoch(jete, the antheridia are produced by certain 

 bodies to which M. Pringsheim has given the name of androspores. 

 These androspores are produced in cells differing from the ordinary 

 vegetative cells only in their small size. The androspores differ 

 hardly at all from the ordinary zoospores of the plant except in 

 being of smaller size, and after their escape from the parent cell they 



* See Jahrbiicher fiir wiss. Bot. Vol. i. p. 1. 



