224 SUMMARY OF CURRENT RESEARCHES RELATING TO 



small and irregularly scattered. Reproduction takes place by succes- 

 sive fission ; the entire contents of the capsule divide into from four 

 to thirty-two parts, according to the generation to which the indi- 

 vidual belongs. The cilia persist and the movements of the individual 

 are not interrupted until from fifteen to thirty minutes before the 

 emergence of the young or fission-products, when the cilia disappear ; 

 the maternal envelope gradually dissolves, while the young move over 

 each other ; they each have a delicate investing membrane. The first 

 generation divide into eight, the second into four (forming the 

 macrogonidia of Cienkowski). About ten days after an infusion 

 is made the results of the division into four themselves divide into 

 thirty-two small individuals (microgonidia) ; both ends of the latter 

 are usually pointed. There is no morphological difference between 

 the macro- and microgonidia, for the shape of both is essentially the 

 same, as is best seen by comparing microgonidia resulting from a 

 division into sixteen with the fusiform macrogonidia. 



After a short free existence, the microgonidia copulate in pairs ; 

 the pair are usually equal in size, but not unfrequently a large 

 individual unites with a small one ; contact is first eifected by the 

 anterior cilium-bearing ends ; the cells then apply themselves longi- 

 tudinally to each other, fusing and forming a heart-shaped mass 

 which in from fifteen to thirty minutes ceases moving and has become 

 a globular cell about ' 008 mm. in diameter ; the cilia then disappear, 

 and the cell grows to a diameter of • 013 to • 015 mm., when it con- 

 tains a tolerably large green amylone globule and is invested by 

 a strong rigid membrane. Stein has wrongly interpreted certain twin 

 gonidia as showing stages of an act of conjugation, whereas they 

 are distinguishable from coj)ulating gonidia by being united by the 

 middle or posterior, not by the anterior ends, and by the consequent 

 persistence of the cilia. If the round cells produced by copulation are 

 dried and then moistened with water the contents divide into four 

 pieces which form young Cldorogonia and become free. 



Chlorogonium must be removed from the Astasicea owing to its 

 want of contractility, its developmental history, and manner of 

 fission. It seems referable, as Reinhard has observed, to the 

 Volvocina, on the following grounds : — Its possession of an investing 

 capsule, its successive divisions within the capsule, the motion by 

 means of two incessantly active cilia, and the coj)ulation resulting in 

 round resting-cells. It seems especially allied to Polytoma by its 

 incessant motion, by several details in the mode of fission, and by the 

 fission first into eight and after that always (except in the last 

 division) into four. 



