98 SUMMARY OF CURRENT RESEARCHES RELATING TO 



cells, hundreds or thousands of which are associated together into a 

 spherical mulberry-like mass, but not enclosed in a gelatinous en- 

 velope. The cells are not more than 2 /a in diameter, but are pro- 

 vided with a relatively thick hyaline membrane, enclosing a black or 

 chocolate-brown protoplasmic body. A pair of vibratile cilia pass 

 through the membrane, and the whole mass is in active motion, 

 revolving round its centre. In some cases the cilia have disappeared, 

 and the mass has become immotile. The mass measures 8-10 /x in 

 diameter when it consists of about 100, 30-40 /^ when it consists of 

 1000 cells. Beyond this size it elongates into an oval form, becomes 

 constricted in the middle, and then divides into two, both freely 

 endowed with motion. There is no chlorophyll in the cells. Placed 

 in sunshine in water containing carbonic acid they do not disengage 

 carbonic acid. They sometimes assume a violet or reddish colour. 



Besides the division of the mass, there are two other modes of 

 multiplication. When the mass has attained its full size, the cells 

 of which it is composed sometimes completely separate from one 

 another ; those at the periphery, which have retained their cilia, con- 

 tinue to move about, while those towards the centre, which have lost 

 their cilia, are motionless ; while in other cases all the cells are 

 motionless. Each cell then multiplies into two by the ordinary pro- 

 cess of cell-division ; and the process is indefinitely repeated. The 

 daughter-cells sometimes separate completely after each division ; 

 sometimes they gradually aggregate into a mulberry-like mass. The 

 colour of the protoplasm is dark or light blue or dark brown. 



The third mode of multiplication takes place by the thick mem- 

 brane of the separate cells becoming gelatinous, and gradually dis- 

 solving ; the protoplasm remaining in the form of highly refractive 

 colourless spheres or resting-cells. Under favourable conditions they 

 increase in size, a dark blue pigment becomes gradually diffused 

 through the protoplasm ; they become invested with thick membranes, 

 and provided each with two cilia. Under the form of resting-spores 

 the organism can pass through periods of drought or cold. 



As regards the systematic position of this organism, it seems to 

 present the greatest affinity with the Volvocinese, notwithstanding the 

 absence of chlorophyll, and especially with the three genera, Synnra, 

 Syncrypta, and Uroglena, established by Ehrenberg, characterized by 

 the presence of a special colouring matter which masks the chlorophyll. 

 Van Tieghem proposes to establish for it a new genus, and to call it 

 Sycamina nigrescens. It occurs at the bottom of water in ponds and 

 vases in the midst of organic detritus, and disengages a large amount 

 of marsh-gas. 



Gloeocystis.* — This organism has been described by Naegeli as 

 belonging to a low type of organization ; by Cienkowski as nearly 

 allied to the Volvocineae, and by Lohde as exhibiting affinity with the 

 Hydrodictyeae. P. Eichter, who has submitted it again to a close 

 examination, agrees with the first view, considering that the two latter 

 authors had under observation, not the true Gloeocystis, but a condition 



* Hedwigia, xix. (1880) pp. 154-9. 



