TRANSACTIONS OF SECTI.ON D, — DEPT. ZOOLOGY AND BOTANY. 599 



5. Oh tltc Development of Jjepiilostens. . 

 By F. M. Balfoue, F.B.S., and W. N. Parkek. 



The paper contained an account of tlie observations of the authors on some pre- 

 . served material supplied to them hy Al. Agassiz. The following are the chief 

 points to which attention was called : — 



(1) The segmentation is complete as in the Sturgeon, hut the segments at the 

 lower pole of the ovum soon fuse into a single mass which forms the yolk sack. 



(2) The epiblast is divided into a nervous and an epidermic layer. 



(3) The cerebro-spinal cord is formed, from a solid keel-like thickening of the 

 epiblast, as in Teleostei and Petromyzon. In this respect Lepidosteus contrasts 

 strilcingly with the Sturgeon, in which the cerebro-spinal cord is formed in the usual 

 vertebrfite fashion. 



(4) There is a pronephros (head-kidney) of the Teleostean type. 



The authors further called attention to the structure and homologies of a pro- 

 visional suctorial disc in front of the mouth, of which Agassiz has already given an 

 account. 



6. On the Classification of Cryptogams} By Alfred W. Bennett, M.A., 

 B.Sc, F.L.8., Lecturer on Botany at St. Thomas's Hospital. 



In the most recent classification of cryptogams, that by Sachs, in the 4th ed. 

 of his ' Lehrbuch,' he divides thallophytes (including characeaj) into four classes of 

 equal rank, Protophyta, Zygosporete, Oosporete, and Oarposporere. It is proposed 

 in the present paper to retain Sachs's class of Protophyta for the lowest forms of 

 vegetable life ; but to restore the primary division of the remainder of thallophytes 

 into fungi and algte, as being more convenient to the student and at least as much 

 in accordance with probable genetic affinities. 



As regards minor points, the characete are removed altogether from thallo- 

 phytes, and again constituted into a separate group of the first rank ; the myxo- 

 mycetes are regarded as presenting a low type of structure, scarcely raised above 

 the protophyta, and not exhibiting true sexual conjugation ; volvox and its allies 

 are removed from the zygosporete to the oosporese; and the phaeosporeae are 

 .separated off as a distinct order from the fucacere. 



The thallophytes are therefore iirst of all divided into three primary classes : — ■ 

 Protophyta, Fungi, and Alg^e. The protophyta are divisible into two sub- 

 classes, Protomycetes and Frotophycece. The protomycetes consist of a single 

 order, the Schizomycetes, of which saccharomyces is regarded as an aberrant 

 form. The protophycejB are composed of the protococcacese (including palmellacese 

 and scytonemacere), nostocacefe, oscillatoriese, and rivulariese. The Myxmnycetes 

 are treated as a supplement to the protophyta. The fungi are made up of three 

 sub-classes, employing in the main the same characters as Sachs, but, in their 

 terminology, using the syllable 'sperm ' instead of 'spore.' The first division, the 

 Zyyomycet.es (or zj'gospermete achloropliyllace£e), is composed of the mucorini 

 only (including the piptocephalidfe). The second, the Oomycetes (or oospermese 

 achlorophyllacece), comprises the peronosporete aiid saprolegniese (including the 

 chytridiaceoe). The third, the Carpomycetes (or carpospermese achlorophyllace.'e), 

 is made up of the uredinese, ustilagineie, basidiomycetes, and ascomycetes, the 

 lichenes being included in the last as a sub-order. The algfe are arranged under 

 three corresponding sub-classes. The Zyyophycece (or zj-gospermete chloro- 

 phyliaceae) is made up of the following orders: — Pandorineae, hydrodictyeae, con- 

 fervacete (under which the pithophoraceae may possibly come), ulotrichaceae, 

 ulvaceae, botrydieae, .and conjugatae (the last comprising the desmidieae, diato- 

 maceae, zygnemaceae, and mesocarpeae). The Oophycece (or oospermeae chloro- 

 phyllaceae) include the volvocinese, siphoneae (with the nearly allied, dasycladeae), 



' Published in cxtcnso in the Quarterly Jovrnnl of Microscojncal Science, for 

 Oct. 1880. 



