240 DR. p. CnALMEIlS MITCHELL OX THK 



These appenr to me to vary considerably from individual to 

 individual, but the most notable of them are an attachment of 

 the omentum to the part where the distal limb of the pendant 

 loop bends round to pass into the rectal portion of the hind-gut, 

 and various attachments between the duodenum and the colon. 



In 1905 I summed up the description of the gut-pattern in 

 Prosimia? as follows : — " The duodenum is seldom well distinct 

 from Meckel's tract ; the latter varies in length, probably in 

 relation to diet. The caecum is always present, and is usually 

 very capacious. The hind-gut (except in Tarsius, where it is 

 extremely reduced and still shows signs of former diffei-entiation) 

 is relatively extremely long, sometimes being as long as, or 

 longer than, the fore-gut. It is, moreover, of greater calibi'e. 

 It shows a well-marked colic region which may be a long narrow 

 loop, or a complex set of folds, and a distinct rectum." I now 

 add to this a few points. The duodenum is frequently marked 

 ofl" by its greater calibre. The hind-gut is much reduced iii very 

 small Lemurs such as Chirogaleus and Microcvhus \ in others it 

 shows a definite ansa coli de.vtra developed from the distal 

 portion of the pendant loop, usually long, narrow, and straight 

 in Chiromi/s and Lemur, wider and more irregular and tending- 

 to be spiralh" twisted in at least most other genera. An ansa 

 coli sinistra, shorter and usually wider than the ansa devtra, is 

 frequently present on the proximal part of the rectum. 



Order Simi/R. 



I have no new ol^servations to report, although I have 

 examined a number of other Apes and Monkeys. For con- 

 venience I may quote my former summary (Mitchell, 1905, 

 p. 515): — "The duodenum and Meckel's tract together form a 

 series of loops which differ from group to group in their lelative 

 complexity, arranged round about three-quarters of the circular 

 outgrowth of mesentery. The ca?cum is always present and 

 appears to have been originally capacious and of nearly equal 

 calibre throughout its length ; but it is in process of shortening 

 throughout the group, being, as a rule, shoi'ter in the Old World 

 Monkeys than in the New Woi'ld Monkeys and Anthropoid 

 Apes (if in the latter case the vermiform appendix be leckoned 

 with the caecum). The state of the ease may be put in anothei" 

 way. The originally long, capacious caecum of the Simife is 

 retained by the greater number of the Platyrrhine Apes ; in the 

 Catarrhine Apes, except the Hylobatidae and Anthropomorphse, 

 it tends to become shorter without the formation of a vermiform 

 appendix. In the two groups last named, its proximal portion 

 has remained capacious, but the greater part of its original 

 length has been transformed without shortening into the thick- 

 walled vermiform appendix." 



I should add to this that the presence of a rather well- 

 pronounced transverse colon is the normal condition in the group. 



