io8 Recent Literature. [zoe 



ization. The opening pages review Guignard's discovery of the 

 " attraction spheres " and " centrosomes," structures long known 

 in animal cells, but not hitherto certainly demonstrated in those 

 of plants. These Strasburger regards as essential constituents 

 of the cell, and therefore assumes that they must take part in 

 fertilization, which can no longer be regarded as consisting in 

 the union of the sexual nuclei alone. 



Before passing to the consideration of the zoospores the author 

 describes for the first time the occurrence of the attraction spheres 

 in an alga — Sphacelaria scoparia — in which he found these easily 

 demonstrable, and concludes as they have been found in so many 

 widely diverse forms, that they are probably always present when 

 there is a separation of the protoplasm into cytoplasm and nucleus. 

 For the protoplasm radiating from the centrosomes, and that 

 composing the spindle-fibres and connecting threads of the kary- 

 okinetic figures, he proposes the name "kinoplasm," and sup- 

 poses it to play an important part in nuclear division. 



The development of the zoospores w^as carefully studied in a 

 number of algae belonging to different groups. The most impor- 

 tant conclusions reached were that the transparent end of the 

 zoospore is composed of kinoplasm that gives rise to the cilia 

 which are formed as outgrowths from it. The envelope in which 

 the zoospores are often contained when first ejected from the 

 mother-cell, is the outer protoplasmic layer {Haidschichf) of the 

 mother-cell, and not part of the cell-wall as hitherto supposed. 



Comparing the development of the non-sexual zoospores with 

 that of the gametes or sexual ones, and also of the spermato- 

 zoids of higher cryptogams, he points out clearly the common 

 nature of all these forms. In Chara fragilis, according to his 

 account, the forward, cilia-bearing coils of the spermatozoid, orig- 

 nate as a cytoplasmic appendage of the nucleus, and the hinder 

 coil is also of cytoplasmic origin, and corresponds to the hinder 

 granular part of a zoospore. Only the middle coil is composed of 

 nuclear substance, instead of the whole body of the spermatozoid 

 as has been supposed. The forward coil gives rise to the cilia in 

 the same way as the clear forward end of a zoospore does, and 

 like that he considers this to be composed of kinoplasm. In 

 mosses and ferns, only the small forward coils of the spermato- 



