we have at last gained a clue to the source whence 

 the Vertebrata were derived. We should then be 

 justified in believing that at an extremely remote 

 period a group of animals existed, resembling in 

 many respects the larvae of our present Ascidians, 

 which diverged into two great branches— the one 

 retrograding in development and producing the 

 present class of Ascidians, the other rising to 

 the crown and summit of the animal kingdom by 

 giving birth to the Vertebrata. 32 



Baer cited after this only one negative treatment of 

 Kovalevsky's discovery, 33 an d with characteristic honesty he 

 drew attention to its groundlessness. Baer's objectivity 

 stands out here more clearly, since he himself did not 

 agree with the opinions of Kovalevsky, Kupffer, and Darwin. 

 In the next twenty pages of his article, he brought all his 

 learning and all his authority to bear on the idea of the 

 relationship between tunicates and vertebrates and attempted 

 to prove their systematic nearness to the bivalves, agreeing 

 in this with Cuvier and basing his ideas upon the situation 

 of siphons, nervous ganglia, and so on. Baer confirmed in 

 particular that the side of the body where the nervous 

 ganglion of ascidians is present is not the dorsal, but the 

 ventral; therefore the nervous system of ascidians could not 

 be homologous to the central nervous system of vertebrates. 

 Later he discussed the cord in the caudal part in the larvae 

 of ascidians and also refused to recognize its homology with 

 the spinal cord of vertebrates. All polemics were sustained 

 in very correct tones. Of his scientific opponents Baer 

 everywhere spoke in a tone of complete respect to their 

 scientific services and high competence. 



Afterwards Baer explained why he went into anatomical 

 details in this article, where it might better have been 

 limited to brief reminiscence. "I meant," Baer wrote, "to 



32. Charles Drawin, THE DESCENT OF MAN, AND SELECTION 

 IN RELATION TO SEX. rev. ed. (New York, 1883), 



pp. 159-160. Russian translation edited by I. M. Sechenov, 

 S0CH.,Vol. 5 (Izd. AN SSSR, 1953), pp. 268-269. 



33. ARCH. ANAT. PHYSIOL. (1870), p. 762. 



482 



