Notes on Recent Literature. 
232 
He is inclined to accept the view of Claussen that, after all, there is 
in this group only one nuclear fusion, that in the ascus. This view, 
however, rests on no sure foundation; even if there were some doubt 
as to the behaviour of the coenogametic Ascomycetes there can be no 
doubt about the presence of both sexual and ascus fusion in forms 
like Sphcerotheca, Erysiphe and Phyllactinia. It is somewhat 
surprising that the Bonn professor should put forward such a view, 
for the work of Harper on Sphcerotheca —which first placed the 
sexuality of Ascomycetes on a firm footing—was done in his own 
laboratory. 
Strasburger then deals with the question of the fixity of the 
diploid and haploid chromosome-number. He points out that no 
case of a phanerogam is known with the haploid number throughout 
its life-cycle and even in the pteridophyta the only known case of a 
haploid sporophyte is that of Nephrodium molle which was artificially 
induced to develop in the haploid state from an apogamous 
prothallus; the spore-formation of this form is not yet known. In 
animals, on the other hand, apart from artificially induced forms, 
cases are known where a haploid generation is a normal part of the 
life-cycle. Strasburger refers to the important work of F. Meves on 
the spermatogenesis of bees and wasps, which ought to be known to 
all botanical cytologists. The males are produced from unfertilised 
eggs in these cases,- and so we find no normal first division of the 
spermatocytes. In the honey-bee this division passes through the 
prophase and reaches the spindle-stage, but the elements of the 
nuclear plate do not separate but show l’egression, while the cytoplasm 
cuts off a non-nucleate polar-body (Richtungskorper). The first 
meiotic division, which should be heterotypic, is thus merely a 
cytoplasmic division; the second division occurs and is of the 
normal type. Such a case as this indicates the close correlation 
between fertilization and reduction. In the fact that in these cases 
the first division (even after the first stages have been passed 
through) is omitted, but not the second, Strasburger finds support, 
as will many other cytologists, for the view that these males possess 
instead of a double series of homologous pangens only a single set. 
In the absence of a double set the division which separates the 
homologous ones is excluded. In such cases as this we find additional 
evidence, though in the nature of the case purely circumstantial, of 
the importance of the nucleus as the carrier—probably the sole 
one—of the pangens, and of the probable close relation between 
segregation and the reduction division. 
In the final section of his work, Strasburger reasserts his belief 
that the nucleus is the sole carrier of hereditary properties and 
refers again to his very convincing observations in 1908 on the 
male nuclei of the pollen-tube, which he showed were quite naked 
and thus could carry into the egg no definite portion of cytoplasm. 1 
In the last few paragraphs very interesting views are put 
forward on the phylogeny of the nucleus and its relation to karyo- 
kinesis. The mitotic mode of division is found constantly in the 
Metazoa and Metaphyta, but not so generally in the lower organisms. 
’ The observations of Godlewski on merogony in echinoderm 
eggs (which are sometimes quoted against the view that the 
cytoplasm plays no part in carrying the pangens), Strasburger 
in agreement with Boveri, does not consider convincing, as 
the embryos were not reared beyond the early stages. 
