ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 231 



quence of sexual union, since otherwise the number of chromosomes 

 would double in each sexual generation. Every gamete carries, in itself, 

 from its origin and nature, the principle of parthenogenetic development. 

 Before conjugation, gametes are nothing but hungry zoospores. If they 

 can satisfy their hunger by direct nutrition, they do not conjugate, but 

 develope non-sexually. Parthenogenesis is simply a continuance of 

 non-sexual multiplication, where the food-supply is ample. When this 

 fails, the gametes devour one another ; and this is sexual reproduction. 



De Toni's Sylloge Algarum. — We have received vol. iv. sect. 2 of this 

 valuable work. It is devoted entirely to four families of the Florideae, 

 viz. the Sphaerococcaceae, Rhodymeniaceae, Delesseriaceae, and Bonne- 

 maisoniaceae ; these four, together with the Khodomelaceae, constituting 

 the order Rhodymeninae, with the following diagnosis: — Cellula carpo- 

 gonii fecundata tili seu processus brevis ope cum cellula auxiliari con- 

 juncta (copulata) ita ut cellula auxiliaris ipsa fertilis evadat et in 

 gonimoblastum versus exteriorem thalli regionein evolvatur ; fila articu- 

 lata carpogonifera et cellulae matres cellularum auxiliarium binatim 

 insimul disposita, saepissime in procarpium proprium conjuncta. The 

 characters of the genera and species are worked out with the usual care 

 and copiousness of reference. 



Fungi. 



Position of Fungi in the Plant System.* — Dr. H. L. Bolley, in 

 reference to the position of the Fungi in the vegetable system, puts the 

 question whether, if putrefying orgauisms be true vegetables, that is, 

 ones which live only on mineral elements, what place should be assigned 

 to the Bacteria and Fungi in the system of plants ? Shall we, he says, 

 continue to call organisms which are so close in nature as to be able 

 to live directly upon mineral elements, even in the absence of sunlight, 

 degenerates ? If these organisms do construct their bodies directly from 

 mineral elements, would it not be a sounder principle to derive the Algae 

 from the Fungi, than vice versa by degeneration ? 



Sexuality of Fungi. I — Mr. H. Wager gives a succinct account of 

 the knowledge hitherto obtained regarding a sexual process in the 

 various families of Fungi, especially in the Phycomycetes, Ascomycetes, 

 and Uredineae, and gives the following general conclusions. 



In the Phycomycetes we have a true sexuality, consisting in the 

 fusion of two nuclei derived from separate more or less completely 

 differentiated cells. In its essential character it does not appear to 

 differ from that of higher plants and animals. Before fusion takes 

 place there may or may not be a preliminary division of the sexual 

 nuclei ; there is not sufficient evidence whether or not this preliminary 

 division is connected with chromosome reduction. Before fusion, the 

 two nuclei, which at first may differ very much in size, attain the same 

 size and staining reactions. Fusion may take place at once, or may be 

 delayed until after germination has taken place. The fusion of nuclei 

 takes place in the resting condition, or possibly in some cases in the 

 chromosome stage. The formation of sexual organs depends, to some 

 extent, on external conditions. Centrosomes have not been observed to 



* Ccntralbl. Bakt. u. Par., 2" Aht., v. (1899) pp. 857-9. 

 t Ann. of Bot., xiii. (iS99>pp. 575-97. 



