OF THE PHTTOZOA. 171 



the Chhnii/dococcus-ce]ls look hairy (var. setiger, V. Flotow). They are 

 merely prolongations of the colourless protoplasm forming the substance of 

 the primordial cells, and correspond pretty well morphologically to the reticu- 

 lated branching filaments of protoplasm, the sap-currents as they are termed, 

 which maintain the nucleus suspended freely in the interior of the cells of 

 the articulations of Spirogyra or of the haii's of the anthers of Tradescantia. 

 Alcohol and acids cause these prolongations to be retracted into the substance 

 of the primordial cells ; the same thing takes place diu'ing the coiu'se of the 

 development. Ehi^enberg has called these peculiar mucous rays, which also 

 occur in some other Volvocinece, in some cases a tail (Sgnura, Uroglena), in 

 others connecting canals or indications of a vascular system (in Volvox and 

 Gonium). These protoplasm-iilaments naturally present a different aspect 

 according to the shape and arrangement of the primordial ceUs : wliile they 

 appear as a wreath of cilia in the globular Chlamydococcus-eeH, in the more 

 spincUe-shaped Stephanosphcera they rather resemble bundles of rays passing 

 out fi'om each end ; in Volvox, if seen only from above, they give the indi- 

 vidual primordial cells a polygonal, radiating aspect, and form threads of 

 communication between them : Focke has wrongly considered them as inter- 

 cellular passages between the individual animalcules. The connecting threads 

 in Gonium, on the other hand, are something quite different, and do not belong 

 at all to the domain of the j)rotoplasm-filaments, as I shall explain more fully 

 at another opportunity. 



" Thus the microscopic analysis, like the chemical investigation, of Steplia- 

 nosplicera, in exact analogy mth Chlamydococcus and the swarming- cells of 

 the other Alga3, has enabled us to distinguish aU the characters of a plant, 

 but not one mark of a true animal organization, in particular not a trace of a 

 mouth, stomach, and sexual organs. But the genus Steplianosphcera is thereby 

 pre-eminently important for the decision of the question of the limit between 

 the animal and vegetable kingdom, because the history of its development affords 

 the most convincing proof of the vegetable nature of this genus, and thus of all 

 the other Yolvocinese. 



" Development of Stephanosphcera. — Both the very delicate envelope-cell 

 and the widely distant, transparent, green, globular, primordial cells of the 

 young Stephanosphcera are of a relatively small size. Both grow so much as 

 to double their dimensions dimng their vegetation : the former acquii-es a 

 tough membrane; the latter fill up the greater part of the envelope- ceU, 

 advance towards each other so as to touch, develope thicker, denser contents, 

 and assume most curious forms through the ramification of the protoplasm- 

 filaments. FinaUy the process of propagation shows itself in the primordial 

 cells. The radiating ends retract aU theii' prolongations, and become rounded 

 into a perfect sphere ; the primordial cells are now merely attached to the 

 envelope-ceU by theii- cilia, and thus are readily moved from their normal 

 corresponding positions, and then appear devoid of any definite arrangement 

 in the envelope- ceU. 



'^ These changes take place in the com-se of the afternoon ; towards evening 

 more influential metamorphoses make their appearance. The primordial cell, 

 namely, extends itself predominantly in one direction in the axis perpendicular 

 to the equatorial plane, consequently in the position wliich represents from 

 above dovvnwards. The two chlorophyll-utricles respectively repair to the 

 two ends ; the green contents likewise flow chiefly to the two sides, and leave 

 a broad colomless zone visible in the middle, such as we observe somewhat in 

 the same position in Closferium. Finally the primordial cell becomes con- 

 stricted, gradually from the periphery to the centre, in the middle line, and 

 is thus divided into two secondary cells, the septum of which, in the position 



