a2 ©. CLIFFORD DOBELL. 
the conception of an originally doubly nucleate cell. This 
hypothesis is much older than the chromidial idea, and is 
intimately bound up with speculations regarding the origin 
of the centrosome. I will try to sketch its history as briefly 
as possible, and then say something about its most recent 
developmental phase. 
In 1891 Biitschli noticed a chromatin-staining centrosome 
in the diatom Surirella, and suggested that it might possibly 
be homologized with the micronucleus of an infusorian. A 
somewhat similar view was advanced by R. Hertwig (792). 
He said that the ordinary nucleus of a metazoan cell might be 
regarded as a nucleus with little or no active substance, but 
rich in chromatin—the centrosome, however, as a nucleus 
which had lost its chromatin but retained its activity. This 
would thus presuppose the original cell to contain two nuclei. 
Lauterborn (’95), continuing Bitschh’s work on diatoms, 
also pursued the ideas which the latter had started. Before 
he had given a complete exposition of the result at which he 
had arrived, however, Heidenhain (’94) published an elabora- 
tion of Butschh’s original conception. He regarded the con- 
dition seenin the Infusoria 
a cell containing two nuclei—as 
a primitive condition, and regarded the nucleus and centro- 
some of a metazoan cell as derived from the infusorian 
meganucleus and micronucleus respectively. As Lauterborn 
pointed out, this is in the highest degree improbable, as the 
arrangement seen in the Infusoria is a highly specialised one, 
and not primitive. 
Lauterborn himself gave a full exposition of his views in 
1896. Asa starting point he takes, not the specialised binu- 
clear condition seen in Infusoria, but a cell containing two 
exactly similar nuclei, Amceba binucleata Gruber 
(Schaudinn, ’95b). From this primitive condition the mega- 
nucleus and micronucleus of Infusoria, and the nucleus and 
centrosome + central spindle of Metazoa, are supposed to have 
been collaterally evolved, Lauterborn supposes that in 
diatoms also the centrosome + central spindle represents one 
original nucleus, Paramceba eilhardi (Schaudinn, 796) 
