66 SUMMARY OF CURRENT RESEARCHES RELATING TO 



(1) Plankton tables ; (2) General remarks on the plankton ; (3) The 

 species' found in plankton, and their distribution, and remarks on the 

 new or critical forms. In the first section the organisms found in the 

 plankton samples, which were collected in 1899 and 1900, are arranged 

 in tables in which the locality, the date of collecting, the depth, the 

 salinity, the temperature, and the more or less common occurrence of 

 the observed species, are given. In the second section the author deals 

 with the question as to the origin of the large masses of diatoms which 

 occur in the spring. He criticises the views of Gran, and suggests other 

 explanations, which are too long to give here in detail. In the third 

 section many useful remarks are made on the definition of the species. 

 A key is published of the plankton forms of Coscinodiscus, and a new 

 species is described. Critical remarks are made on Thalassiosirae. 

 Among the Peridinese the author has worked out specially the genera 

 Peridinium and Ceratium. The new and critical species are illustrated 

 by three large plates. 



Dictyotacese and Aglaozonia.* — C. Sauvageau publishes some in- 

 teresting observations on three species of Zonaria, Z. flava, Z. variegata, 

 and Z. lobata, which he has studied at Teneriffe in a living state. He 

 describes their structure aud reproductive organs, and the results of his 

 experiments with germinating spores. Finally, he describes a new 

 species of Aglaozonia, A. canariensis, which is in appearance very much 

 like Zonaria variegata. It also resembles a Zonaria in structure, and in 

 its reproductive apparatus. The sporangia of A. canariensis are less 

 numerous, and are scattered and pyriform, like the Zonaria species 

 mentioned above ; and in these points A. canariensis shows an affinity 

 to Zonaria and the Dictyotacese, which is not found in so marked a 

 degree in the other species of Aglaozonia. In pointing out this affinity 

 the author does not dispute the view that Dictyotacese and Cutleriacese 

 are quite distinct from one another ; but he does dispute the validity of 

 the group Cyclosporeae, arguing that the presence of a voluminous 

 non-motile oosphere does not suffice to warrant the placing of Dictyo- 

 tacese and Fucacese in the same group. He regards these two orders 

 as extreme developments of two divergent series arising from lower 

 filamentous Phseosporese. 



On the Colouring Matter in Phaeophycese.t — M. Tswett criticises 

 the work of Molisch on this subject, and sums up his remarks as follows. 

 The pre-existence of phycophasin in living brown algse, although ex- 

 tremely unlikely, is not finally disproved by the experiments of Molisch. 

 The assumption that a special modification of chlorophyll (phasophyll) 

 exists in the chromatophores of the brown algse is not justified. The 

 colouring matter of Fucus consists of chlorophyllin a, chlorophyllin y 

 (Sorby's chlorofucin), carotin, and fucoxanthin. Molisch's leucocyan 

 is identical with fucoxanthin. 



Periodicity of the Sexual Cells in Dictyota dichotoma-l — J. Lloyd 

 Williams has made a careful study of this interesting subject, and has 



* Soc. Sci. Arcachon, viii. (1905) 16 pp. 



t Bot. Zeit., lxiii. (1905) pp. 273-8. 



X Ann. of Bot., xix. (1905) pp. 531-60 (6 diagrams in text). 



