McAllister. — Nuclear Division in Tetraspora fabric a. 683 
chromosomes — about thirty in number — arise from the reticulum indepen- 
dently of the nucleole. A distinct bipolar spindle, with no traces of 
a centrosome or centrosphere, appears at metaphase. In one respect only 
— the persistence of the nucleole — is there any divergence from typical 
division as known in the higher plants. The nucleole, according to Nemec, 
becomes much elongated, the two resulting parts remaining connected by 
a slender strand of nucleolar material. Not until the daughter nuclei are 
partly formed does this connecting strand disappear. The main elements 
of the nucleus, as well as of the method of nuclear division, are the same in 
this Alga as in the higher plants. 
Tuttle (50) has recently confirmed the earlier work of Strasburger (45), 
Wille (52), and Mitzkewitsch (35) on nuclear division in Oedogonium , and 
has published a fuller account of mitosis in this Alga than any one of these 
investigators. His results clearly show the origin of a spireme thread from 
a reticulum, independently of the nucleole, — the formation of the chromo- 
somes from this spireme, and the splitting of these and the distribution of 
the split halves to the daughter nuclei, where they become reconverted into 
the reticulum of the new nucleus. The nucleole forms no morphological 
part of the chromatic thread or the chromosomes. It is interesting to note 
that here the spindle is intranuclear. 
Timberlake’s work (48) on Hydrodictyon dealt with very minute nuclei 
and a small number of phases of division. Nevertheless, as he says, 
‘ enough stages stand out sharply to show that the process is essentially 
the same as in the higher organisms. 5 A spireme is formed from the 
reticulum. This segments to form about ten chromosomes. These pass 
into the equatorial plate stage. Two groups of chromosomes are formed, 
probably by the splitting of each of the ten original chromosomes, although 
this splitting was not observed because of their very small size. Centrosome- 
like bodies are described and figured at the poles of the spindle figure. 
Yamanouchi (59) has recently published a short note upon what he 
regards as a new species of Hydrodictyon from South Africa. A brief 
reference is made to nuclear division. He is of the opinion that the spindle 
is intranuclear and has centrosomes, — but his few small, diagrammatic 
text-figures certainly do not go far toward establishing the presence of 
centrosomes for this species. He refers to numerous chromatophores which 
‘ have two functions, one to produce characteristic pyrenoids and the other 
to form reserve starch grains ’. Starch formation was not observed in 
connexion with pyrenoids but it is formed, perhaps by secretion, in the 
plastids near one margin. If this brief reference is substantiated by more 
exhaustive investigation, we have in this Alga, plastids which cause starch 
deposition in a manner apparently identical with that in the seed plants, — 
the pyrenoid not functioning as a starch-forming cell organ. 
Allen’s research on Coleochaete (1) has shown that the reduction 
