62 Prof. C. Glaus on the 



The interpretation of the antennae also I am said to have 

 taken from Prof. l?lay Lankester's writings ! In his Cell- 

 layer publication of the year 187'i our author has set up the 

 beautiful hypothesis * of the change of position of the buccal 

 aperture in the Arthropoda in order to explain a second sup- 

 position of his, according to which the prostomiura of the 

 Arthro])oda is formed exclusively by the eye-segment. Ray 

 Lankester consequently assumes that the anteinial segments 

 were originally placed metastoraially, and only became pro- 

 stomial by a subsequent shifting of position of the oral aper- 

 ture. In what "way, and induced by what causes, the forma- 

 tion of the new mouth took place we unfortunately do not 

 learn ; but we are told that this assumption is /w//y warranted 

 by Kowalewsky's investigations upon Amjy/iioxus, because, 

 according to his observations, the mouth of Amphioxus is the 

 first gill-slit or pharyngeal j^erforation on the left side, and 

 has no relation to the primary larval mouth &c. (see footnote). 

 Thus it is a completely false analogy which is supposed to 

 furnish the foundation for the notion of the " adaptational 

 shifting of the oral aperture," and justify the interpretation of 

 the Arthropod antennae as postoral limbs. And yet Ray 

 Lankester ventures now to call this completely futile specu- 

 lation a fundamental theory^ from which I am supposed to 

 have borrowed the interpretation of the second Crustacean 

 antenna as a body-appendage ! Subsequently, in the Limidas- 

 article and that on A pus of the year 1881, the postoral nature 

 of the antennse is again affirmed, but only for the Crustacea ; 



* This fine passage runs as follows: — "Much more likely it seems is 

 the explanation that the oral apertnre shifts position, and that the oph- 

 thalmic segment alone in Arthropoda represents the prostomium, the 

 antennary and antennular segments being aboriginally metastomial, and 

 only prostomial by later adaptational shifting of the oral apertnre." 

 An^ further on (but upon this he has, perhaps wisely, said nothing) : 

 " The assumption of such a shifting of the oral aperture is fully warranted 

 by what has been demonstrated iu the case of Vertebrata through 

 Kowalewsky's researches on Amiihioxus. It is certain from those 

 observations that the month of Amphioxus is the first gill-slit or pharyn- 

 geal perforation of the left side, and has no relation to a mouth such as 

 that which appears at an earlier stage of development in the allied 

 Ascidian larva, which latter mouth is that of Vermes generally. A^nphi- 

 oxus then and the Vertebrata have a new oral aperture, the old one being 

 gradually suppressed. Comparative osteology and the embryology of 

 higher Vertebrata have long made it clear that the vertebrate mouth 

 belongs to the series of visceral clefts ; but the significance of this in the 

 comparison of Vertebrata and Invertebrata has yet to be fully appreciated. 

 The identification of the neural and haemal aspects of Vertebrata and 

 Vermes iu the light given by this demonstration of Kowalewsky's, as to 

 the distinct chaiacter of the mouth in the two cases, must lead to most 

 valuable results." 



