134 
.1. r. HII;L v\ND CHAS. IF. o’dONOGHUE. 
PAGE 
Pseudo-Pregnancy ..... L53 
Uterine Changes ..... 154 
Metcestrus ...... 130 
Summary . . . . . . 160 
Conclusions ...... 165 
1. Comparison of (Estral Cycles in the Metatheria and 
Eiitlieria . . . . . .165 
2. The Monoestrons and Polyoestroiis Conditions . . 169 
List of References . . . . .171 
Description of Plates . . . . .174 
Introduction. 
In recent years a great deal of attention has been paid to 
tlie reproductive processes in the Mammalia, and in particular 
to the phenomena connected with the oestral cycle. Observa- 
tions relating to the latter, however, have been almost 
entirely based on Eutherian mammals, and, indeed, largely 
on Primates (Heape (8, 9, 10), Van Herwerden (12), Hitsch- 
mann and Adler (15), and others) and various domesticated 
or semi-domesticated Eutheria (e.g. sheep (16), dog (19), 
ferret (17), Marshall). Having at onr disposal a large volume 
of records relating to the breeding habits of Dasyurus, as 
well as an abundant supply o£ material, we have thought 
that an inquiry into the reproductive cycle in thisme)nber of 
the Marsupialia (in many respects a more primitive group 
than the Eutheria), might not only be of interest, but might, 
perchance, throw light on some of the problems relating to 
the Eutherian cestrous cycle which still await solution. We 
venture to liope that the account of the reproductive cycle 
which we are now able to present will be found to fulfil, in 
some measure, expectations in this latter regard. 
We desire to say here tha.t our work has been greatly 
facilitated by the circumstance that some of the phenomena 
relating to reproduction in Dasyurus have already been 
described in greater or less detail (Hill (13, 14), O’Donoghue 
(20, 21), Sandes (22)). 
The breeding season has been divided up into periods for the 
