TRANSACTIONS OF SECTION K. 815 
It is, however, quite possible that the protease here described as ‘ tryptic’ 
may be found to be a mixture of erepsin with a pepsin. 
4, Sexuality in Zygospore Formation. By Dr, A, F, BuaKESLEE. 
1, The production of zygospores in the Mucorinew is conditioned primarily 
by the inherent nature of the individual species, and only secondarily by external 
factors. 
2, According to their method of zygospore formation, the Mucorinee may be 
divided into two main groups, which have been termed respectively homothallic 
and heterothallic. 
3. In the homothallic group, comprising the minority of the species, zygo- 
spores are developed from branches of the same thallus or mycelium, and can be 
obtained from the sowing of a single spore. 
4. In the heterothallic group, comprising probably a large majority of the 
species, zygospores are developed from branches which necessarily belong to thalli 
or mycelia diverse in character, and can never be obtained from the sowing of a 
single spore. 
5. These sexual strains in an individual species show in general a more or 
less marked differentiation in vegetative luxuriance, and the more or less luxuriant 
may be appropriately designated by the use of (+) and (—) signs respectively. 
G. In heterothallic species, strains have been found which from their failure 
to react with (+) and (—) strains of the same form have been called ‘neutral,’ 
and a similar neutrality may be induced by cultivation under adverse conditions, 
7. In all species of both groups in which the process of conjugation has been 
carefully followed, the swollen portions (progametes) from which the gametes are 
cut off do not grow toward each other, as currently believed, but arise from the 
stimulus of contact between more or less differentiated hyphae (zygophores), and 
are from the outset always normally adherent. 
8. In some species the zygophores have been demonstrated to be mutually 
attractive (zygotactic). 
9. In the heterogamic subdivision of the homothallic group a distinct and 
constant differentiation exists between the zygophoric hyphz and the gametes 
derived from them, but in the remaining homothallic forms and in all hetero- 
thallic forms no such differentiation is apparent. 
10, A process of imperfect hybridisation will occur between unlike strains of 
different heterothallic species in the same or even in different genera, or between a 
homothallic form and both strains of a heterothallic species, 
11. By taking advantage of this character it has been possible to group 
together in two opposite series the strains of all the heterothallic forms under 
cultivation. 
12. When thus grouped the (—), or less luxuriant strains, will be in one series, 
while the (+), or more luxuriant, will be in the other. 
13. From the foregoing observations it may be concluded :— 
(a) That the formation of zygospores is a sexual process ; 
(b) That the mycelium of a homothallic species is bisexual ; 
(c) While the mycelium of a heterothallic species is unisexual ; 
(d) And, further, that in the (+) and (—) series of the heterothallic 
group are represented the two sexes. 
5. Some General Results on the Localisation of Alkaloids in Plants. 
By Professor L. ERRERA. 
Microchemistry does not claim in any way to supplant chemistry. Its great 
value consists in permitting an approach to problems unattainable by ordinary 
analytical methods, and in accomplishing for physiological (and also for petrographic) 
