THE EAE,LY DEVELOPMENT OP THE MARSUPIALIA. 3 



if necessary to daily examination. ^ But it has this great dis- 

 advantage, which it apparently shares with other Marsupials, 

 that a very variable period intervenes between coitus and 

 ovulation. As a consequence, the obtaining of any desired 

 cleavage or early blastocyst stage is largely a matter of 

 chance.^ It is true that the changes which take place in the 

 pouch, in correlation with ovulation and the events connected 

 therewith, do afford in the case of late pregnant females some 

 indication of the stage of development likely to be met with, 

 but these changes are at first of too indefinite a character to 

 be of much service beyond indicating that ovulation may have 

 taken place. 



Dasyurus breeds but once a year, the breeding season 

 extending over the winter months — May to August. One 

 remarkable feature in the reproduction of Dasyurus, to which 

 I have directed attention in a previous paper (Hill, '00), may 

 be again referred to here, and that is the fact that thei-e is no 

 correlation between the number of ova shed during ovulation 

 and the accommodation available in the pouch. The normal 

 number of teats present in the latter is six, though the 

 presence of one or two supernumerary teats is not uncommon; 

 the number of ova shed at one period is, as a rule, far in 

 excess of the teat number. I have, for example, several 

 records of the occurrence of from twenty to twenty-five eggs, 

 two of twenty-eight, one of thirty, and one of as many as 

 thirty-five! (twenty-three normal blastocysts and twelve 



^ Perameles, on the other hand, though quite common in many parts 

 of the State, is hy no means such a convenient type It is much less 

 easily trapped than Dasyurus, does not live nearly so well in captivity, 

 and is particularly difficult to handle. I have to thank Mr. D. Gr. Stead, 

 now of the Department of Fisheries, Sydney, for first directing my 

 attention to the breeding habits of Dasyurus, and also for providing 

 me with the first female from which I obtained segmenting eggs. 



^ Tor example, I oljtained unsegmented ova from the uteri, four, five, 

 six, seven and eight days after coitus, 2-celled eggs six and seven 

 days after, 4-ceUed eggs eleven and eighteen days after. In one case 

 the young were bom eight days after the last observed act of coitus, 

 in another sixteen days after, and in yet another twenty days after. 



