The distribution and number of Peyer's patches (5) in two species of marsupial 
mice, Antechinus swainsonii and Antechinus stuartii was found to be the same 
even though the length of the intestine in the latter species was half that of 
the former. Both species lack a caecum and appendix. The position of the Peyer's 
patches is unusual in that the first three Peyer's patches are on the right side 
of the small intestine whereas the penultimate and ultimate Peyer's patches are 
large, contain many lymphoid follicles and are in an anti-mesenteric position in 
the small intestine and sometimes in the large intestine (ultimate Peyer's 
patch). The number of Peyer's patches in eutherian mice of similar size, and 
intestinal length is greater (13) although the number of Peyer's patch lymphoid 
follicles per centimeter intestine is less (1.8) than in A. swainsonii (4) and 
A. stuartii (4.4). Marsupial mice have most of their lymphoid follicles confined 
to a few large Peyer's patches, whereas eutherian mice have fewer lymphoid 
follicles per unit intestinal length, more Peyer's patches (with fewer lymphoid 
follicles) evenly distributed along the intestine and more single lymphoid 
follicles interspersed between them.