Cytology of a new variety of A chly a americana, 175 
When we have full knowledge of the karyology of Ulothrix , 
Oedogonium , Coleochaete , &c., we shall be able to see how far 
this tentative view is justified. On Strasburger’s view, for 
example, Aglaozonia cells should have twice as many chro- 
mosomes in their nuclei as the cells of Cutleria. On the view 
explained here the number should be the same. 
Summary. 
1. The nucleus in Achlya americana var. camhrica is 
bounded by a nuclear membrane, and possesses a central 
body of spongy texture. This contains chromatin and 
nucleolar matter. It is neither a nucleolus nor a chromosome. 
The space between the nuclear membrane and the central 
body is occupied by nucleo-hyaloplasm and traversed by fine 
threads of linin. 
2. The nucleus undergoes divisions in the mycelium, and 
the nuclei produced in this way ultimately pass into the 
sporangia and gametangia. 
3. Neither nuclear divisions nor nuclear fusions take place 
in the sporangia. 
4. In the oogonia and antheridia many at least of the 
nuclei undergo division by a typical indirect method, the 
number of chromosomes being probably four. 
5. No nuclear fusions take place in the gametangia. 
6. The supernumerary nuclei in the gametangia are got 
rid of by digestion or simple degeneration. 
7. In my opinion fertilization takes place. The naked egg 
has one central nucleus ; oospores with very delicate investing 
cell-walls have two nuclei, one peripheral, near to a fertili- 
zation-tube, the other central ; oospores three days old have 
one central large nucleus. The entrance of the male nucleus 
into the egg takes place when both gameto-nuclei are in 
the stage of anaphasis. The fusion of the gameto-nuclei 
takes place some time after they have assumed the resting 
condition. 
8. The oospore may germinate as soon as ripe, or remain 
in the resting condition without loss of germinating power 
