364 A. A. W. HUBREOHT 



rically placed and of a general internal metamerisation, 

 but differing from Giinda in such important respects as the 

 presence of the forerunners, both of the hypophysis and of the 

 notochord, two structures no trace of which is found in the 

 salt-water Triclades. Such Platyelminths must needs 

 have resembled the present Nemertines more than 

 anything else. 



Here the important question at once thrusts itself upon us : 

 Has the formation of a coelom already been arrived at in the Ne- 

 mertines or not? i.e. have these animals a body-cavity developed 

 out of and separated from the primitive digestive tract or not ? 

 Although I have formerly, when attempts were made to bring 

 theNemertines under the so-called Parenchymatous Flat-worms, 

 combated those attempts, and endeavoured to show that the 

 regular arrangement of digestive and generative caeca, the deve- 

 lopment of muscular septa between them, Sec, went contrary to 

 it, yet now that our ideas about the significance of a true body- 

 cavity as an ultimate derivate of the archenteron have of late 

 years gained so considerably in clearness and definition, I 

 should hesitate to affirm that any such body-cavity is present 

 in Nemertines, and would be inclined to answer the question 

 proposed above negatively. 



Both in the more highly differentiated Hoplonemertini and 

 in the more primitive Schizo- and Palseonemertini, I have 

 met with numerous instances in which all the space which 

 remained free between the muscular body-wall on the one 

 hand, and the intestinal, generative, proboscidian, and circu- 

 latory cavities on the other, was one unbroken mass of con- 

 nective tissue. 



Sometimes, more especially around the oesophagus, occurred 

 what were apparently fissures and cavities in this tissue. They 

 were not lined by an epithelium (are perhaps in communica- 

 tion with the vascular system ?), and could best be compared 

 to a true Schizocoelom (Huxley), i.e. fissures in a mesoblastic 

 tissue. 



All this makes me very much inclined to look upon the 

 alimentary diverticula of the Nemertines in the same light as 



