Timberlahe — 8warm-Spores of Hydrodictyon^ 487 



in Hydrodictyon but, as will appear later, without giving a 

 full or accurate account of the important details. Klebahn 

 (15) has also briefly described a similar process in Spliaeroj)- 

 loea annidina. In this case irregular clefts are said to arise in 

 the protoplast and by further growth and branching to sepa- 

 rate it into the final cleavage products. The origin of the 

 clefts Klebahn does not describe'. 



To Schmitz (21) and Strasburger (23) is due the credit 

 for establishing the presence and peiTnanency of numerous 

 nuclei in many loweT Algae, especially such forms as Hydro- 

 dictyon, Cladopliora, etc., as well as many of the lower Fungi, 

 but the structure and division of the nuclei so far as the coen- 

 ocytic green Algae are concerned, are practically unknown 

 with the exception of Fairchild's (8) work on Valonia and 

 more recently that of Klebahn on S phaeroploea. 



In Kairchild's account of nuclear division in Valonia, there 

 is described and plainly figured for the first time stages showing 

 very clearly that the mitotic division in that plant is similar 

 in its essential features to the nuclear division in the higher 

 plants and animals. 



The chromatin collects into a thread and segments into 

 chromosomes that are collected into an equatorial plate. The 

 daughter chromosomes are dra^\Ti to the poles of the spindle 

 where thev foiTii the dau2:hter nuclei in a manner similar to 

 that observed in most cells. The method of spindle formation 

 was not made out in detail, but at the time of the formation 

 of the equatorial plate the fil^res were seen to conyerge at two 

 points on opposite sides of the nucleus. Whether centrosomes 

 are present Fairchild could not definitely determine, but his 

 figures show quite well defined bodies at the poles of the spin- 

 dle. Around these bodies numerous short rays radiate forming 

 apparently quite typical a.sters. 



The nuclear membrane persists, according to Fairchild, un- 

 til the anaphases in which it is drawn out into a long sac like 

 structure between the two daughter nuclei. Fairchild saw no 

 trace of the central spindle fibres in connection with this sac 

 like structure. The fact that, in Valonia, amitotic nuclear di- 

 vision may occur in the same cell with the mitotic divisions 



