HISTORICAL REVIEW. 13 



During this same year Lankester ('77) placed himself on record to the 

 effect that members of the genus Neomenia are among the most generalized 

 molluscs, related to the Chitons and C'hitonellus, yet belonging apart in a phylum 

 which he termed Scolecomorpha, the first division of Mollusca eucephala. 



Another of the important papers which appeared during this year came 

 from the hand of von Graff, who investigated the anatomy of Neomenia carinata 

 and reexamined Chaetoderrna )iiti(Juliun. From the facts disclosed this author 

 was ct)nvinced that not only are the two forms constructed u])on the same 

 plan, but that the establishment of the Amphineura as a separate phylum by 

 von Ihering was wholly justified. "Wir erkennen in Neomenia und Chaeto- 

 derma Modificationen einer sehr alten Urform, vom denen die letztere naher den 

 Wiirmer, die erstere naher den jMollusken anknlipft." In (|uite a remarkable 

 way the facts discovered in the study of these two species supported von Iher- 

 ing's contention that the Solenogastres and the Chitons are allied forms, though 

 they did not force one to the belief that the Amphineura are necessarily to be 

 placetl in the phylum Vermes, and von Ihering himself abandoned this i)()sition 

 a short time later. 



About the same time Hansen (77) published a most important jiaper on 

 the anatomy of Chaetoderrna nitidulum, and in the treatment of all the systems, 

 especially the urogenital, advanced our knowledge to a considerable extent 

 beyond the old position. For the first time the mode of development of the 

 sex products was determined, and their route traced to the exterior; in other 

 words the broader features of the anatomy of Solenogastres now became com- 

 prehensible. In the opinion of the author, Chaetoderma does not clearly belong 

 to any definite place in the existing system of classification; that while certain 

 moUuscan characters appear, others are strongly suggestive of annelid relation- 

 ships, so that its exact position is yet in doubt. 



The following year Gegenbaur ('78) in the "Grundrisse" made a few very 

 guarded statements regarding the relationships of Neomenia and Chaetoderma 

 which may, provisionally at least, be designated the Solenogastres and may 

 be regarded as a division of the group Vermes. The ventral groove of Neo- 

 menia "represents the first stage in the formation of that pedal surface of the 

 body which is seen in the lowest Mollusca." On the other hand the nervous 

 system, while decidedly different from that in the worms, nevertheless presents 

 some fundamental resemblances. 



With the exception of two or three short notices no other papers appeared 

 until 1881, which in some respects is the most important year in the history of 



