VOLVOCINEiE. 



[ 681 ] 



VOLVOCINE^. 



BiBL. Berk. Brit. Flor. ii. pt. 2. p. 352-3; 

 Ann. Nat. Hist. 2 ser. v. p. 466. pi. 1 1 . fig. 3 ; 

 Greville, Crypt. Fl. pi. 102. pi. 268. fig. 2 ; 

 Corda, Icon. Fung. ii. pi. 13. fig. 107 > Fries, 

 Syst. Myc. iii. p. 447. 



VOLVOCINE^.— A family of microsco- 

 pic organisms which, in agreement with the 

 majority of recent writers on Algology, we 

 have included among the Confervoid Algae, 

 although they have been included until lately 

 among the Infusorial animalcules, among 

 which they form one of Ehrenberg's families. 

 The most striking general character of these 

 objects is, their composition of individual ele- 

 ments which exhibit in their mature and 

 most perfect stage of existence the characters 

 of the transitory zoospores of the other 

 Confervoids. If we exclude from this family 

 the genera Chlamidomonas and Gyges, which 

 we regard as founded upon the zoospores of 

 a plant quiescent in its typical form, the 

 Protococcus of this w^ork, — the Volvoci- 

 nese may be characterized as plants com- 

 posed of a number of permanently active 

 zoospore-like bodies associated together into 

 families of definite form (a kind of " polypi- 

 dom "), in which the members, connected or 

 held together in various ways by cell-mem- 

 branes, retain their distinct individuality 

 for all physiological purposes of nutrition, 

 growth, reproduction, &c., but represent 

 only one being in relation to the surrounding 

 objects. The best known and most beauti- 

 ful example of this family is the genus Vol- 

 vox (PI. 3. fig. 24), consisting when mature 

 of a spherical membranous sac, at the peri- 

 phery of which, within the membrane, are 

 arranged a large number of zoospore-like 

 bodies, each provided with a pair of cilia, 

 which pass out through the enveloping mem- 

 brane, and collectively form a coating all 

 over the external surface, by their vibration 

 causing a rotatory motion of the entire globe. 

 The foreign genus Stephanosph^ra, 

 Cohn, differs principally from Volvox in the 

 fact that the ciliated bodies are only eight in 

 number, and are placed in a circle at the 

 equator of the spherical sac. With regard 

 to Ehrenberg's genera Pandorina, Syn- 

 crypta, Uroylena, Eudorina, and SphcBro- 

 sira, we much doubt whether they are not 

 founded merelj^ on stages of development or 

 abnormal conditions of Volvox; but even if 

 really distinct, they are probably constructed 

 on the same plan. Gonium however is very 

 distinct, and resembles Volvox only in the 

 essential character of the family above laid 

 down. It is composed of a group of usually 



sixteen " zoospores," which are not enclosed 

 in a common sac, but each possesses a thick 

 gelatinous coat or membrane (appearing 

 like a transparent limb or border to the 

 green body, as in Glceocapsa, Coccochloris, 

 &c.), and the individuals cohere together by 

 a few points of the surface of this special 

 coat or "cell-membrane" (PL 3. fig. 11). 

 Ehrenberg's representation of a plate-like 

 continuous coat is erroneous ; our drawing 

 from nature exactly agrees with the older 

 figures, and Cohn's (see Gonium). The re- 

 lations of the doubtful genera above named 

 to Volvox are treated under the article Vol- 

 vox. It may be observed here that there 

 is certainly a close resemblance between the 

 objects termed Chlamidomonas and Gyges, 

 and the constituent individuals of the " fa- 

 mily-stocks " of Volvox, &c., and the nature 

 of the latter is best comprehended by con- 

 sidering them as representatives of the 

 former. But as we have said above, the active 

 Chlamidomonads appear to us to be only 

 transitory stages of a quiescent Alga; for al- 

 though they often propagate by division 

 while active when placed in the sunshine, 

 they ordinarily soon come to rest and 

 grow by a vegetative cell-division if kept in 

 a vessel with sloping borders, or if objects 

 are placed in the water, upon which the film 

 of quiescent Pro^ococcM5 can gradually spread 

 itself up above the edge of the liquid. 



It might be useful to observers to give the 

 characters of all the above genera as laid 

 down in Ehrenberg's work, in spite of our 

 disbelief in their validity, but in so doing it 

 would be necessary to describe them from 

 his drawings, as his written characters are 

 altogether useless, from being founded on 

 false analogies. The red-eye spot is certainly 

 found in Gonium, and probably in all ; we 

 doubt the statements about a single " pro- 

 boscis " (vibratile cilium) ; and the so-called 

 tail, a posterior prolongation of the body, 

 is an obscure character. The tabular ana- 

 lysis which Ehrenberg gives would not en- 

 able any one to distinguish the forms without 

 the assistance of plates. We have therefore 

 prepared a new table founded on his cha- 

 racters and drawings, marking those genera 

 which appear to us really distinct. 



Char. Permanently active zoospore-like 

 bodies, ciliated (except Gyges), surrounded 

 by a gelatinous coat (like Coccochloris), 

 combined in definite groups (or solitary, Eh- 

 renberg), with or without a common enve- 

 loping membrane. Individuals pyriform, or 

 with the body prolonged posteriorly. 



