EARLY RESEARCHES 13 



Huxley is inclined to associate them either with certain 

 degenerate Crustacea, or with the Arachnida (scorpions, 

 spiders, etc.), rather inclining to the latter view. But 

 in his letter to Sir John Richardson he tentatively 

 speaks of them as Annelids, or segmented worms. 



6. " Observations upon the Anatomy and Physiology 

 of Salpa and Pyrosoma" (Phil. Trans. Roy. Soc, 1851, 

 Part 2, pp. 567-94. Annals and Mag. Nat. Hist., ix, 

 1852, pp. 242-4. Sci. Mem. i, vn, p. 38). 



7. " Remarks upon Appendicularia and Doliolum, two 

 Genera of the Tunicata" (Phil. Trans. Roy. Soc, 1851, 

 Part 2, pp. $y$-6o6. Sci. Mem., i, vm, p. 69). 



The last two important memoirs deal with pelagic 

 members of the Tunicata, Ascidians, or sea-squirts, 

 animals which are now known to constitute a lowly 

 group of the Vertebrata. Huxley largely added to our 

 knowledge of their anatomy and physiology, and it does 

 not detract from the merits of his work that parts of it 

 had been anticipated. As in so many of his contribu- 

 tions to science the comparative method of Johannes 

 Miiller was applied with eminent success, and the work 

 on Salpa was of especial interest. For earlier in the 

 century Chamisso discovered in these creatures what he 

 termed " alternation of generations," i.e., the alternation 

 of a sexual and an asexual stage in the same life-history, 

 a phenomenon which is now known to be of frequent 

 occurrence among plants and in several groups of animals. 

 Huxley succeeded in placing Chamisso's conclusions on a 

 firm basis, at the same time modifying and extending them. 



While the memoirs now briefly dealt with, and some 

 others to be subsequently mentioned, were the direct 

 result of Huxley's voyage, the material collected and the 

 observations then made led to other and later contribu- 

 tions to science. 



