RELATION OF THE LANCELET TO THE ASCIDIAN. 44 1 



But just at this time the true connection was discovered 

 in an entirely unhoped-for and most unexpected quarter. 

 Toward the end of the year 1866, among the treatises 

 of the St. Petersburg academy, two works appeared by 

 the Russian zoologist, Kowalevsky, who had spent a long 

 time at Naples, and had occupied himself in studying the 

 individual evolution of some of the lower animals. A fortu- 

 nate accident had led Kowalevsky to study almost simul- 

 taneously the individual evolution of the lowest Vertebrate, 

 the Amphioxus, and that of an Invertebrate, the direct 

 relationship of which to the Amphioxus had not been even 

 guessed, namely, the Ascidian. Greatly to the surprise of 

 Darwin himself, and of all zoologists interested in that 

 important subject, there appeared, from the very commence- 

 ment of their individual development, the greatest identity 

 in the structure of the bodies of those two wholly different 

 animals, — between the lowest Vertebrate, the Amphioxus, 

 on the one hand, and that misshapen lump adhering to 

 the bottom of the sea, the Sea-squirt, or Ascidian, on the 

 other hand. In this undeniable ontogenetic agreement, the 

 existence of which, in an astonishing degree, can be proved, 

 the long-sought genealogical link was, of course, directly 

 found, according to the fundamental law of Biogeny, and 

 that group of Invertebrates, which is most nearly allied to 

 the Vertebrates, was clearly recognized. There can be no 

 longer any doubt, especially since KupfFer and several other 

 zoologists have confirmed and continued these investisja- 

 tions, that of all classes of Invertebrates, the Mantle-animals 

 (Tunicata), and of the latter, the Ascidians, are most nearly 

 allied to the Vertebrates. We cannot say the Vertebrates 

 are descended from the Ascidians ; but we may safely assert, 



