A STUDY OF METAMERISM. 463 



and its segmented tail either an antefact or a secondary 

 acquirement. 



Bateson (3) has attempted to show that Balanoglossus is 

 related to the Chordata, and is unsegmented, I (32) have 

 defended the same supposed relationship, and described 

 Balanoglossus as segmented. Spengel (36) believes Balano- 

 glossus not to be related at all to the Chordata. 



Amphioxus is a typically segmented form, but has given no 

 clue as to the origin of its metamerism. 



By many morphologists (Semper, Dohrn, Van Wijhe, Minot, 

 &c.) the group Chordata is supposed to be derived directly 

 from segmented Annelids. But the Annelid-vertebral con- 

 nection has as many opponents as defenders, and is one of 

 the most illustrious results of the phylogenetic method. 



It must be admitted, of course, that morphologists are 

 dealing with complex and difficult problems in attempting to 

 unravel the past connections between the larger phyla of the 

 animal kingdom, and that their speculations have been in 

 many cases ingenious working hypotheses ; but the results 

 show, I think, that the method is easily carried too far, and 

 that, after many trials, it has not led us to any definite con- 

 clusion. 



Ontogeny has been also fruitful in speculation. The cry 

 has been that Ontogeny tended to repeat Phylogeny, and 

 larval forms without end have been set up as archaic 

 remains. 



The rise, culmination, and decline (?) of the Gastrsea theory 

 illustrates in a concrete case the history of the ontogenetic 

 method ; and the Nauplius theory teaches a lesson of caution 

 that ought not to be forgotten. The coelom theory, built up 

 on the splendid results of Agassiz, Metschnikoff, Kowalewski, 

 Lankester, Hatschek, and Hertwig, while a most suggestive 

 working hypothesis, has led to no settled conclusion; for the 

 well-ascertained fact that in many groups (Sagitta, Amphioxus, 

 Brachiopods, Echinoderms, &c.) gut-pouches give rise to the 

 ccelom has not led us to any decision as to whether we 

 have here an ontogenetic performance or a phylogenetic rape- 



