524 



SYSTEMATIC HISTOET OF THE ESTFUSORIA. 



being specifically distinct. These Cohn has pointed out in his essay ; but only 

 that portion of them is worth citing which has attracted notice in various 

 works. " Thus the still Protococcus-ce\l corresponds to the P. Coccoma (Kiitz.) : 

 when the border becomes gelatinous, it resembles P. pidcJier, and the small 

 cells P. minor. The encysted motile zoospore, on the other hand, is the Gyges 

 Oranulum, and resembles also P. turgidus (K.) and perhaps P. versatilis 

 (Braun). The zoospores divided into two must be regarded as a form of 

 G-yges hi2ycirtitus, or of P. dimidiatus.^^ A red variety of the cell was de- 

 scribed by Girod Chantrans as a Volvox, under the name of Volvox lacustris ; 

 but Perty refers it to Hcermatococciis. 



CwLAMYDOCOCCVS pliwialis. — Sufficiently characterized in the above history. 

 Chl. nivalis. — Unsatisfactorily distinguished. 



Genus GLCEOCOCCUS. — This is a new genus suggested by Braun {On 

 Rejuvenescence, p. 159), who thus describes it : — " Ovate, green cells, with a 

 coloiu'less point, fi-om which a funnel-shaped, lighter space extends inwards ; 

 a rather large vesicle also is formed at the posterior extremity. Multiplica- 

 tion by simple or double, in the latter case decussating fission, after which 

 the ceUs remain loosely connected together by the secretion of soft, gela- 

 tinous, confluent coats, forming globular and finally amorphous famihes 

 (clusters). The cells of all the generations succeeding each other dui-ing the 

 formation of these families (excepting the transitory cells in the case of 

 double halving) are provided vrith two very long persistent cilia, which dis- 

 appear only when division commences. The cells exhibit a feeble motion 

 inside the enveloping and connecting jelly, the anterior end jerking in and 

 out, or suddenly retracting a little. The last generation of the family leave 

 the gelatinous mass, and swarm out, to settle down quickly in some other 

 place. It is probable that the formation of a new family is preceded by a 

 rather long state of rest — perhaps there are several resting generations ; but 

 we have no observation on this point." A red speck is not perceptible. Two 

 species are named : — 



G. minor. — Perhaps specifically di- 

 stinct. Appears in the springs at Frei- 

 bm-g eariy in the year, in the form of 

 light-yellowisli-gTeen, often pear-shaped 

 " stocks " (masses), almost as large as a 

 hazel nut, attached to the sides of the 

 gutters of the springs, finally becoming 

 detached, swimming, and shapeless. The 

 cells are somi 

 millim. long. 



Glceococcus 7m(cosHS. — The fidl- 

 grown cells are 1-60 to 1-50 miUim. 

 long : the clusters, forming at the bottom 

 of little ponds, attain the size of an 

 apple, and are of compressed globular, 

 often lobed-shaped form ; but at length 

 they break up, and come to the sm'face of 

 the water in irregular fragments. The 

 gelatinous mass has a peculiar greenish 

 spotted aspect, which depends upon sub- 

 ordinate groups of generations being 

 more closely packed together. 



Genus SPBL^ROSIRA. — Tail-like process absent ; eye-speck and fila- 

 ment single. Self-division, imlike that in the preceding genera, occurs un- 

 equally ^vithin the envelope, and forms young clusters at once from the parent 

 ones. This genus difi'ers from Pandorina in having the eye-speck, from 

 Eudorina by its unequal mode of self- division, and from Volvox by its 

 simple filament. Self-division in these creatures takes place in the longi- 

 tudinal direction, in parallel planes ; so that laminse are produced, as in the 

 case of Gonium. 



Splicerosira, as heretofore remarked, is regarded by Prof. Busk as a doubtful 

 independent organism ; he is, however, unable to speak positively on this 

 point, and therefore, whilst still keeping it distinct from Volvox Glohcdor, of 



