388 THE AMERICAN NATURALIST. [Vol. XXXVIII. 



which may in the beginning have several poles (see Fig. l,g), 

 but these generally swing at last into a common axis so that 

 the spindle finally becomes essentially bipolar. The term 

 filarplasm is applied to this free fibrillar condition of kinoplasm 

 without organized centers. Filarplasm is peculiar to plant cells 

 and its remarkable activities in connection with multipolar 

 spindles have only been found in groups above the thallophytes. 

 Centrospheres, centrosomes and asters among the lower plants 

 resemble in general the same structures in the animal cell. But 

 filarplasm presents a higher form of kinoplasmic structure with 

 perhaps the most complex activities known in the process of 

 spindle formation. We shall consider them especially in Section 

 III when treating the spore mother cell. 



The blepharoplasts are in some respects the most complex 

 structures derived from kinoplasm. They are most conspicuous 

 in the sperm cells of higher plants (spermatophytes and 

 pteridophytes) but they are undoubtedly present in lower 

 forms and probably in zoospores. The blepharoplast develops 

 cilia as delicate fibrillae from its surface. The origin and homol- 

 ogies of the blepharoplast are uncertain. In some forms they 

 resemble centrosomes at the poles of the last nuclear figures in 

 sperm tissue. But in other cases they are entirely independent 

 of such spindles, a character which cannot be brought into 

 harmony with the activities of centrosomes. They finally lie 

 one at the side of each sperm nucleus, see Fig. 3, h, and with 

 the development of the sperm they follow the spiral twist, when 

 present, as a parallel band (Fig. 2,, h, 2 and 3). This structure 

 will receive detailed treatment in our account of the sperm 

 (Section III). 



2. Non Protoplasmic Contents. 



It is not possible to distinguish with certainty all the non- 

 living material of a cell from its protoplasm. We have at one 

 extreme cells from which the protoplasm has almost or wholly 

 disappeared and which are either entirely empty or set apart 

 solely as receptacles for various substances, sometimes waste 

 products and sometimes food materials. In contrast with this 



