ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 443 



of auxospores he looks on as only occasional modes of reproduction, and 

 not as typical of the whole group. 



With regard to the geographical distribution of diatoms, the author 

 regards it as certain that several distinct floras exist ; although it may be 

 premature to determine finally the question of distribution according to the 

 genera and species that inhabit different areas. The question of the de- 

 pendence of life at great dej)ths in the ocean on the penetration of sunlight 

 is then discussed, as well as the formation of banks and deposits of diatoms. 



The bulk of the volume is occupied with descriptions of the species 

 collected, the immense majority being either new species or new varieties ; 

 each description is accompanied by a plate. The following are new 

 genera : — 



Cyclophora (Pseudoraphidieee). Frustula tabulata, rectangula, in fascias 

 conjuncta, rarius soluta ; isthmo gelineo alterne concatenata ; a fronte 

 linearia vel parum inflata; valvis inajqualibus, quarum una loculo centrali 

 instructa. 



Dactyliosolen (CryptoraphidiesB). Distinguished from Bhizosolenia by 

 the occurrence in the course of the filaments of hyaline belts. Forma 

 cylindrica ; frustulum eompositum ex pluribus annulis cellulatis ; cellulis 

 linearibus oblongis. 



Corethron (Cryptoraphidiese). Frustula cylindrica libera (?) ; valvis 

 convexis, setarum radiantium corona cinctis. 



Willemoesia (Cryptoraphidieee). No diagnosis given. 



Eihmodiscus (Cryptoraphidiese). Frustula solitaria, discoidalia ; valvis 

 tenuissime et inconspicue striolatis ; forma plus minus convexa, quandoque 

 diversimode denticulata, zona connectiva punctulata. 



Reproduction in a Fossil Diatom.* — Count F. Castracane describes 

 the appearance presented by a fossil diatom from Monte Gibbio, which he 

 identifies with Coscinodiscus radiolaius, consisting of the impressions of a 

 great number of closely packed round bodies on the edge of the valve. 

 These he believes to be impressions of embryonal forms still remaining 

 within the mother-cell at the time of its death, exhibiting therefore a similar 

 mode of reproduction to that which he had already observed in the case 

 of PodospTisenia.\ 



Fossil Diatoms from TJmbria.J — Count F. Castracane describes a calca- 

 reous deposit from Spoleto in Umbria, extremely rich in diatoms, especially 

 in species of Epithemia and Cyclotella, of great size and beauty. 



Ijichens. 



Synthesis of Lichens. § — M. G. Bonnier has succeeded in obtaining by 

 artificial culture, in an atmosphere which has been completely sterilized, 

 by the process of synthesis, several species of corticolous lichens, viz. 

 Parmelia Acetabulum and Physcia parietina and stellaris, as well as Lecanora 

 sojphodes and ferruginea among saxicolous species. The constituent alga was 

 a Protococcus or Pleurococcus. Two sets of experiments were made : — in 

 the one set one of these algse, in the other set the gonidia of a lichen, were 

 sown in closed and sterilized cells in conjunction with the hyphsB of a 

 fungus. In the latter case no development took place ; in the former case 

 a true lichen-thallus was obtained under the same conditions. Experiments 



* Atti Accad. Pont. Nuovi Lincei, xxxviii. (1886) 6 pp. and 1 fig. 

 t See this Journal, 1885, p. 1041. 



j Atti Accad. Pont. Nuovi Lincei, xxxviii. (1886) 7 pp. 



§ Comptes Eendus, ciii. (1886) pp. 942-4, and Bull. Soc. Bot. France, viii. (1886) 

 pp. 546-8. 



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