15 



dener with respect to Lichens, that this great section of the 

 vegetable kingdom, which we had thought to be as well de- 

 fined as mosses or Hepaticae, is constituted of nothing else 

 but low forms of Algoe, overrun by ascomycetous fungi, 

 which have become parastic upon them. The principal sup- 

 port of his theory is founded on the similarity in structure 

 between the gonidia of lichens and many unicellular Algoe, 

 and under cultivation it was found that the gonidiai of 

 Evernia and Cladonia continued to propagate and also to pro- 

 duce zoospores. I do not know what our Crombie and 

 Leighton have to say on the matter, but Nylander and 

 Krempelhuber the great continental lichenologists, it is 

 hardly necessary to say, are opposed to it, and no doubt con- 

 tinued observation of the plants throughout all their stages 

 of development, will in time clear up the difficulty. 



In Zoology I must give the highest place to the great 

 work " Die Kalkschwiimme," or Calcareous Sponges, of Ernst 

 Haeckel, in which he gives due recognition to the merits of 

 our English naturalists, Grant, Johnston and Bowerbank. 



Grant first arranged the sponges into three divisions — 

 Ceratospongiae, Silicispongiae, and Calcispongiae ; but while 

 retaining the last, with which alone the present work deals, 

 the author classes the two former together as Fibrospongise, 

 and adds a third division, Myxospongige, for certain gela- 

 tinous forms, as Halisarca. 



In the first volume of 484 pages are detailed the morpho- 

 logy of the Entoderm and Exoderm, the Syncytine or Sar- 

 codous tissue, and the Spicules ; the latter have a simpler 

 nomenclature than that used by Dr. Bowerbank, being 

 arranged in three groups : — 1. Three-rayed ; 2. Four-rayed 

 (each with three divisions — regular, sagittal and irregular) ; 

 and 3. Eod-like, which again embraces bacillose, fusiform 

 and subuliform as single-poled, and clavate, rhopalate, stili- 

 form, hastiform. and perforate as double-poled forms ; then 



