THE DEVELOPMENT OF THE NYMPH. 333 



the nymph, is brought into relation with the posterior extremity 

 of a new metenteron formed by the elongation of the mesen- 

 teron of the nymph. 



The nature and origin of the clear, coagulable fluid which 

 surrounds the ' corpus luteum,' or degenerating larval intestine, 

 is uncertain. It resembles blood, but contains no granule cells. 

 The remains of the larval intestine are seen to be penetrated 

 by and surrounded by leucocytes and multinuclear phagocytes, 

 by which they are ultimately disintegrated. Crystalline sub- 

 stances resembling leucin and tyrosin are also frequently 

 present at a later period. The fluid is absorbed during the 

 later stages of development. 



The chyle stomach, proximal intestine, Malpighian tubes, and 

 metenteron of the imago are all developed from the archenteron 

 of the nymph. (See Alimentary Canal of Imago.) 



g. Origin of the Mesoderm. 



Mesenchyme and Mesoderm. — Unfortunately, whenever a new 

 term is introduced into science, it is years before it attains any 

 definite meaning. A crowd of investigators seize upon it and 

 apply it to every possible appearance which exhibits even a 

 remote resemblance to that for which it was originally coined. 

 Hence the most inextricable tangle of misconceptions originates, 

 I shall not attempt to criticise the various meanings to which 

 the term ' mesenchyme ' has been applied, but to define the 

 exact meaning I ascribe to it in these pages. 



By mesenchyme, or parablast, I mean those groups of cells 

 which have been at one time in their history wandering 

 amoeboid corpuscles, but which may form a continuous rete 

 or network, or an epithelioid layer, and which are either 

 converted into connective tissue, return to their amoeboid 

 form, or remain as amoeboid cells. Whether these cells are 

 budded off from the blastoderm, or whether they are the off- 

 spring of yelk ceUs derived directly as amoeboids from the 

 mother organism, may remain an open question ; but that they 

 exist in the food yelk is beyond doubt, and unless they become 



