596 MR. F. E. BEDDARD ON THE ANATOMY OF [May 26, 



those orders where they occur, that is to say the Rodentia, 

 Perissodactyla, Artiodactyla , Hyracoidea, and Lemurs, there is no 

 relation between complexity of coils and length of gut. The 

 small Rodent Arvicanthis has a short colon not longer than that 

 of many mammals of other groups without any trace of coils. 

 And yet it possesses one ansa, the postcascalis. The existence of 

 three ansae in the Beaver does not ai^gue a longer colon than in 

 the Agouti, where there is only one ansa, the ansa coli dextra. 

 The complex spiral of Inch'is is not associated with a mai'kedly 

 longer colon than that which bears the one loop of the genus 

 Hyrax. It is therefore clear that we must seek for the origin of 

 these fixed loops of the colon in some other way than need for 

 packing away a large tract of gut in a limited space. And it has 

 been already suggested that this may be found in the attachment 

 of the omentum. 



Value of Intestinal modijications in Classification. 



Apart from certain facts given by Weber and others as dis- 

 tinctive of various groups of Mammals, Dr. Mitchell seems to be 

 the only person who has attempted to discuss in detail the' 

 classificatory results to be obtained from a consideration of the 

 varying characters of the intestinal tract. In a pi'eliminaiy 

 criticism of resemblances — an attempt to diflerentiate those upon 

 which weight should be laid from those which cannot be admitted 

 as of classificatory imjjortance, this author has committed himself 

 to a statement that will not receive the agreement of zoologists. 

 " Likenesses " he writes (on p. 528) " which are due to the common 

 possession of primitive features cannot be regaided as evidence 

 of near relationship ; that certain membeis of a group have 

 retained what was once the pi-opeity of all the members of that 

 grovip can be no reason for placing such creatures close together 

 in a system if that system is to be based on blood-relationship." 

 It is, I imagine, by absolutely universal consent that Echidna 

 and Ornithorhynchus are placed together in one order, Mono- 

 tremata, and mainly by virtue of the facts that in both there 

 is a large coracoid and a generally " primitive " shoulder-girdle : 

 that in both the egg is large-yolked and meroblastic with a 

 follicle of at most two layers of cells : that in both the anterior 

 abdominal vein is either present or indicated by a large ventral 

 mesentery : that in both the heart valve of the right auriculo- 

 ventricular ostium has retained the partly musculai- structui'e of 

 that of lower types ; and by other features all of which are 

 primitive. 



One can of course accede to Dr. Mitchell's assertion that the loss 

 of a particular character in two groups is no reason for placing them 

 in proximity, and that a new structural acquisition is evidence of 

 relationship in proportion to the anatomical complexity of that 

 structure ; this latter is a perfectly correct restatement of Sir E. 

 Ray Lankester's use of the Molluscan Odontophore as a test for 



