A TA VISM OR RE VERSION. 141 



thalmite was exopoditic, whilst the inner portion, which 

 furnished the antenniform process, was endopoditic in 

 character. 



The interest of this specimen lies in the fact that it is 

 exactly analogous to the conversion of an element of a 

 flower, say a stamen, into a leaf. Although I have made 

 a wide search, nothing in any way comparable to this 

 specimen can be found recorded in zoological literature, 

 but there can be little doubt that such cases occur if we 

 would watch for them. One would also imagine that 

 similar malformation must occasionally occur in the 

 appendages of insects, but thus far my inquiries have 

 not had any material result. 



From organs we turn our attention to tissues, and 

 examine some specimens illustrating the reversion of 

 mucous membrane to skin. 



The exterior of our bodies is covered by a membrane 

 called skin, which differs in many points from that 

 lining the internal cavities the mouth, stomach, and 

 intestines and known as mucous membrane. The 

 contrast between skin and mucous membrane is well 

 illustrated in the case of the conjunctiva, the delicate, 

 sensitive membrane covering the eyeball and ocular 

 aspect of the eyelids. The conjunctiva is really modified 

 skin, and not infrequently declares its ancestry by 

 reverting to its original form. Indeed, it is no unusual 

 event to find a patch of hair-covered skin growing upon 

 the ocular conjunctiva. Such cases are far from rare. 

 Mr. T. Collins is of opinion that about twelve cases of 

 this abnormality are seen annually at the Ophthalmic 

 Hospital, Moorfields. These dermoid patches are most 



