THE BALANOGLOSSUS THEORY 287 



together with the formation from the ectoderm of a dorsal 



o 



nerve tube. 



Bateson's views attracted considerable attention, and were 

 thought by many to lighten appreciably the obscurity in 

 which the origin of Vertebrates was wrapped. Thus 

 Lankester wrote in his article on Vertebrates l in the 

 Encyclopedia Britannica : " It seems that in Balanoglossus -we 

 at last find a form which, though no doubt specialised for its 

 burrowing sand-life, and possibly to some extent degenerate, 

 yet has not to any large extent fallen from an ancestral 

 eminence. The ciliated epidermis, the long worm-like form, 

 and the complete absence of segmentation of the body- 

 muscles lead us to forms like the Nemertines. The great 

 proboscis of Balanoglossus may well be compared to the 

 invaginable organ similarly placed in the Nemertines. The 

 collar is the first commencement of a structure destined to 

 assume great importance in Cephalochorda and Craniata, 

 and perhaps protective of a single gill-slit in Balanoglossus 

 before the number of those apertures had been extended. 

 Borrowing, as we may, the nephridia from the Nemertines, 

 and the lateral in addition to the dorsal nerve, we find that 

 Balanoglossus gives the most hopeful hypothetical solution 

 of the pedigree of Vertebrates." 



Much doubt was cast upon the Chordate affinities of the 

 Enteropneusta by Spengel in his monograph of the group, 2 

 but when the development of the ccelom came to be more 

 thoroughly worked out in Balanoglossus and Amphioxus, 

 the striking resemblance in this respect between the two 

 forms gave additional support to the Batesonian view. 3 



1 Reprinted in Zoological Articles, London, 1891. 



2 " Die Enteropneusten des Golfes von Neapel," Fauna und Flora 

 des Golfes von Neapel, Monog. xviii., Berlin, 1893. 



3 See Macbride, "A Review of Prof. Spengel's Monograph on 

 Balanoglossus," OJ.M.S., xxxvi., 1894, and "The Early Development of 

 Amphioxus," Q.J.M.S., xl., 1898. 



