114 



THE AMERICAN MONTHLY 



[June, 



by means of the cilia of the indi- 

 vidual cells. 



Sexual propagation by oogonia and 

 antheridia. The latter form by the 

 enlargement of single vegetative cells, 

 the contents givir>g rise to sperma- 

 tozoids. The oogonia are produced 

 by the enlargement of other vegeta- 

 tive cells. When ripe the oosphere 

 is surrounded only w^ith a gelatinous 

 covering. The spermatozoids pene- 

 trate the latter and the fertilized 

 sphere becomes covered w^ith a thick 

 membrane. After a period of rest it 

 germinates. 



Asexual multiplication by division 

 of vegetative cells of considerable 

 size (parthenogonidia) . giving rise to 

 new families, which separate from 

 the mother-family as soon as the cilia 

 are developed. 



Synopsis of Genera. 



Families spherical, cells in berry-like 



mass, within thin hyaline envelope. 



Eudorina^i 51. 



Family a hollow sphere, with green 



cells regularly disposed within the 



surface. Volvox., 52. 



51. Genus Eudorina Ehrenberg. 



Families ovate, usually of t6 or 32 

 cells, within a hyaline, gelatinous en- 

 velope ; cells spherical, with thin 

 membrane, each with 2 cilia, green, 

 colorless in front, with a starch grain, 

 pigment spot, and 2 pulsating vacu- 

 oles in the colorless end. Cells evenly 

 spaced around the outside of the 

 sphere, the cilia projecting as in 

 Volvox (52). 



Antheridia form in the four an- 

 terior cells of the family, the remain- 

 ing 28 cells producing oogonia. 

 Oospores red, smooth or somewhat 

 stellate. 



Asexual propagation by division of 

 vegetative cells into 16-33 daughter- 

 cells, which at first are united into a 

 goniutn-Vike., tabular family (48), 

 afterwards becoming spherical. 



\_Eudorina and Pandorina are 

 scarcely different enough to make two 

 genera. In the latter the common 

 envelope and the membranes of the 



individual cells are rather thicker 

 than in Eudorina. The shape of 

 the Eudori?ia family is described as 

 oval, that of Pattdorina globose or 

 sub-globose, but this character is not 

 of much value, or even constancy. 

 The process of sexual reproduction 

 may serve as a distinction for the 

 time, but it is jorobable that Pando- 

 rina also propagates in the same 

 manner. It has been stated that 

 Eudorina is dioecious.] 



52. Genus Volvox Ehrenberg. 



Family consisting of many cells, 

 spherical, continually rotating, re- 

 sembling a hollow globe with green 

 cells regularly disposed just within 

 the surface, each with 2 long cilia 

 projecting through the common, hya- 

 line envelope, a red spot, and two 

 pulsating vacuoles. 



Sexual propagation by biciliated 

 spermatozoids formed within special 

 cells, and oogonia, forming red 

 oospores. 



Asexual propagation forming new 

 families within the parent sphere, 

 by division of certain cells. These 

 are set free by the rupture of the 

 parent sphere. 



[ Volvox may well be regarded as 

 the highest type of this interesting 

 family. There are two species gener- 

 ally recognized which are distin- 

 guished by their difference in size, 

 V. globator and V. minor. The 

 former is dioecious, the latter mono- 

 oecious.] 



\^To be continued^ 



Grermicides and Antiseptics. 



In a lecture before the Biological 

 Society of Washington some time 

 ago Dr. Geo. M. Sternberg, U. S. A., 

 gave the following lists of germicides 

 and antiseptics. A germicide is an 

 agent which destroys the life of an 

 organism. It may be able to kill 

 only the actively growing organism, 

 or it may also kill the spores. Anti- 

 septics may not be germicides. They 

 may only prevent the growth of or- 

 sranisms without killing them. 



