Minot.] 18 [November 15, 



be at one of the most important points of divergence, and the study 

 of them has therefore a greater interest than hitherto. Prof. Semper 1 

 has recently traced a relationship between Annelids and Vertebrates, 

 and the study of other classes of worms reveals many much discussed 

 connections with other higher animals. It has become, therefore, a 

 matter of importance to see in what way worms are related to the 

 lower divisions of animals. As the Plathelminths have long been 

 regarded as the lowest form, I undertook an investigation of the 

 anatomy of the Planarians. 



The result of this study has been the conclusion that these animals 

 are much more highly organized than is usually supposed. It has been 

 frequently stated that some, or all parts of these worms are formed by 

 a protoplasmatic substance, and not of cells, and a relationship with 

 the Infusoria has therefore been supposed to exist. I have found, 

 however, that all the tissues are formed by cells, and therefore we 

 .must drop the idea of a connection existing between the Turbella- 

 rians and any of the Infusoria, which, so far as we know, are all uni- 

 cellular, as has been demonstrated by Butschli.' 2 The cells that 

 earlier naturalists did not detect have since been carefully described 

 by Keferstein, Moseley, Graaf, etc. At the time I began my investi- 

 gations, about a year ago, it was still supposed that the parenchym 

 was not cellular, but since then I have discovered that in twenty , 

 different species of Plathelminths it is mainly composed of ramified 

 stellate cells, whose processes intertwine and unite adjacent cells. 

 The general appearance is strikingly similar to that of the embryonic 

 connective tissue in Vertebrates, as seen, for example, in the tail of 

 young tadpoles. 



Mecznikow 3 has asserted that the digestive tract is not a canal, 

 but a solid albuminous cord, as in the Infusoria. He did this with so 

 great positiveness, that no one except Graaf 4 has since ventured to 

 vigorously oppose this view. Mecznikow mistook the nutritive matter 

 with which the digestive canal of these greedy animals is always filled, 

 for an albuminous cord ! and though he describes the cells forming 



iArbeiten des Zoot.-Zool. Inst. Wiirzburg. Bd. II., 1875-76. 



2 Studien Tiber die ersten Eutwickelungsvorgange der Eizelle, die Zelltbeihmg 

 und die Conjugation der Infusorien. Abb. Senkenberg. Natforscb. Gesell., x, 223. 

 Frankfurt a. M., 1876. 



s Ueber Geodesmus bilineatus nob. Bull. Acad. St. Petersb., IX (1865), p. 433. 



* L. Graaf. Zur Kenntniss der Turbellarien. Zeitschr. fur wiss. Zoologie, 

 XXiv (1874), p. 125 (vide p.134, note 2). 



