154 



THE AMERICAN MONTHLY 



[August, 



tasia {hcBmatodss); Phacus (Jxmgi- 

 canda). 



Order 2. Thecoflagellata, H. 

 Sheathed flagellates. Flagellates 

 without a chaplet of cilia; body 

 enclosed by a sheath or shell. 

 The flagella come out from an 

 opening of the shell. Often the 

 shell is fixed upon a stationary 

 pedicle. 



Genera : Salpingmca {marina); 

 Dinobryon {sertularia). 



Order 3. Cilioflagellata, J. 

 Miiller, Flagellates with a circlet 

 of short cilia about the middle of 

 the cell-body ; the latter is enclosed 

 in a bivalve shell. Between the 

 two halves of the shell, issue the 

 long whip and the chaplet of 

 cilia. 



Genera : Peridinium,{oculatuni\ 

 Oeratium {tri^us). 



Order 4. Cystoflagellata, H. 

 Bladder flagellates. 



Flagellates without cilia, with a 

 great bladder-like cell-body, which 

 besides the flagellum has a peculiar 



lash-like appendage, and a staff-like 

 mass within. 



Genera : Noctiluca {milia/ri8\ 

 SeptodisGus {rrtedusoides). 



Class v.— CATALACTA, H. 



One-celled organisms which are 

 joined for a time into a coenobium, 

 but afterward live separate. The 

 coenobia are swimming, jelly-like 

 balls, made up of numerous cells 

 which are joined in the centre of 

 the ball ; vibrating cilia issue from 

 the surface. The hermit-cells (mon- 

 ocyta), which arise from the break- 

 ing up of the coenobia, at first move 

 by swimming like the flagellates, 

 afterwards they change into creep- 

 ing, amoeba-like cells, and finally 

 draw together into a globe and be- 

 come surrounded by a capsule. 



A new coenobium arises within 

 this capsule, by repeated cell-di- 

 vision, and is finally set free. The 

 catalactas are found both in the sea 

 and in fresh- water. 



Genera : Magosphm^i {planula) ; 

 Synura {uvdla). 



The Simplest Forms of Life.— IV. Family Volvociiia. 



Individuals spherical, containing chlorophyll, with two cilia on one end, one or 

 two (seldgm three) contractile vesicles within, which can usually only be seen during 

 perfect rest, with nuclei and pigment spot, in families or single, enveloped with 

 transparent jelly, from which the cilia extend. Colonies have a rolling movement. 

 Individuals united in families in gelatinous envelope, 

 families spherical, 



ball hollow, individuals in the periphery, Volvox. 



ball solid, with 4-64 individuals within, Pandorina. 



ball solid with 8 individuals within, Stephanospheera. 



families tabular, four cornered, Gonium. 



Individuals living singly, Chlamidomonas, 



I. Gen. Voh)ox, Ehr. Individuals 

 spherical, small, in the circumfer- 

 ence of a large, hollow, gelatinous 

 ball, which is formed by the close 

 pressing together of the gelatin of 

 the individuals. The latter produce 

 daughter-colonies by cell division, 

 which are pressed into the interior of 

 mother-cell and perfect themselves. 

 There is besides this a kind of 

 Hexual reproduction, which was ob- 



served by Stein and Busk, but 

 which has been more carefully stu- 

 died by Cohn and Carter. Lai-ge 

 colonies develop certain individuals 

 as females, others as males. The 

 foiTner are the larger and elongate 

 without dividing. The males divide 

 into a large number of linear bo- 

 dies, which are to be regarded as 

 spermatozoids (from a botanical 

 stand-point as microgonidia). They 



