54 2 
Fraser and Brooks. — Further Studies on the 
the forms of the chromosomes. These differences he regards as indications 
of the fact that each type of chromosome forms the physical basis of 
a different set of characters. Lachnea stercorea is an instance among 
plants of a corresponding arrangement. 
The ascogenous hyphae (Fig. 37) in Lachnea are small, and we have 
not been able to count the chromosomes. 
In spore-formation in Lachnea the lines of cleavage are not so much in 
evidence as in Ascobolus. The usual dense and presumably altered mass of 
cytoplasm is present around the centrosome (Fig. 50), and, as usual, it 
increases in size (Fig. 51), and constitutes the spore-plasm. It is traversed 
and defined in Lachnea by astral rays which are finer but more numerous 
and better marked than in Ascobolus . Vacuoles corresponding to the lines 
of cleavage are, however, not without effect, and in the stage shown in 
Fig. 53 a clear space surrounds the aster and perhaps helps to cut out the 
lower part of the spore. 
Discussion. 
The observations detailed above show that in each of the forms 
investigated two reduction-divisions take place. The first mitosis in the 
ascus has in every case the familiar characters of the heterotype division, and 
reasons have been elsewhere adduced (Fraser and Welsford ( 9 )) for regard- 
ing this type of reduction as associated with fertilization or its equivalent. 
The second division follows rapidly on the first, and— -at least in Humaria 
rutilans and Lachnea stercorea — is without special features ; it seems justi- 
fiable therefore to accept it as homotype, and as completing the longitudinal 
fission of the spireme initiated in the heterotype prophase. 
The third division differs little from a vegetative mitosis, but in its 
telophase the number of chromosomes is seen to be half that present on the 
heterotype spindle, consequently the third division has been recognized 
as bringing about a second reduction, and has been termed brachymeiosis. 
This standpoint has recently been criticized by Strasburger ( 18 ) ; he thinks 
it unlikely that two reductions should take place in the ascus, holding 
it more probable that, as Claussen 1 ( 3 ) suggests, there is only one fusion in 
the life-history of Ascomycetes. He doubts that reduction would take 
place in one division or without a contraction phase. It is, therefore, of 
interest that in some of the forms described both at this time and in 
a previous paper ( 9 ), the third division is initiated by a stage comparable to 
the 4 first contraction ’ of meiosis. Where this occurs, the reduced number 
1 Claussen ’s view has recently received confirmation from Schikorra (17), who has seen male 
nuclei enter the ascogoninm of Monascus but considers that their association with the female nuclei 
is of the nature of an approximation and not a fusion. Like Claussen he considers that the 
associated nuclei travel in pairs up the ascogenous hyphae and fuse in the ascus. He brings forward 
no evidence as to the reducing divisions in the ascus and his evidence with regard to the absence of 
fusions in the ascogoninm is of course entirely negative. 
