176 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



much nearer than in the typical form, (3) the strong reticulation of the 

 jjlates. In all these respects the Victoria Nyanza Ceratiuna conies near 

 to C. cornutum (Ehbg.) Clap. & Lachm. In my former paper on Vic- 

 toria Nyanza plankton, following West, as I had not seen any entire and 

 undamaged specimen, I have considered it as merely a form of C. hirun- 

 dinella, hut now, when I have examined better material, I must admit 

 that its diversity from the type is so great that it deserves at least vari- 

 etal rank.^ 



With regard to the arrangements of the plates which have not been 

 given by either of the two earlier observers, my drawings (pi. 2, figs. 15 

 and 16) show that the arrangement is quite typical (see C. A. Kofoid, 

 Zool. Anzeiger, 1907, 32). I have also given a drawing of a speci- 

 men with its plasma protruding as a spherical body outside longitudinal 

 furrow (pi. 2, fig. 17). All the few specimens observed were found in 

 this condition, which remind us of the observations on copulation in 

 Ceratium liirundinella first described by E. Zederbauer (Ber. Deutschon 

 Botan. Ges., 1904, 22, p. 1-8, pi. 1). The specimens observed varied be- 

 tween 150 n and 1G5 /a in length. 



B. Bacillariales. 



The plankton Diatoms present in the samples are Nitzschia nyassensis 

 0. Mllll., Steplmnodiscus astraea (Ehbg.) Grun., Cymatopleitra solea 

 (Breb.) W. Sm., with several varieties, some forms of Surirella, and two 

 species of Melosira. 



Cymatopleura solea occurs in the following varieties which apparently 

 ai'e connected through intermediate forms : 1. typica, 2. suhconstrida 0. 

 Mllll., 3. clavata 0. Mllll., 4. laticej^s 0. Mlill., and 5. nyauzae G. S. 

 Westpro sp. 



Surirella. The many handsome forms of this genus have attracted 

 tlie attention of all former observers. In his excellent paper on tlie 

 Kyassa Diatoms Professor Otto Mliller treats them in great detail and 

 describes a number of new species from Lake Nyassa and adjacent lakes. 

 G. S. West also records many species from Lake Nyassa, from Victoria 

 Nyanza, and from Lake Tanganyika; he points out (/. c, p. 1G5) with 

 regard to some of the species that there occur intermediate stages be- 



1 Trof. Charles A. Koford has kiiiflly drawn my attention to a form de- 

 scribed by A. Hempel (Bull. Illinois State Lab. Nat. Hist., 189G, 4, p. 314, pi. 

 25, lig. 11 and 12, pi. 26, fig. 13) as Ceratium hrevicorne ; it resembles our form in 

 many respects but differs according to the description and the figures in others, 

 f.g., the position and shape of the short second antapical horn; and I hesitate to 

 consider the two forms identical. 



