CORRESPONDENCE WITH L. AGASSIZ 



bryozoa, of which there are also a good many new here. 

 The mollusks have been his favorites for several years 

 past, and he has lately published an excellent revision of 

 the Testacea of New England, particularly valuable for the 

 extensive observations he has collected upon their geo- 

 graphical distribution and the depths at which they occur. 

 When you receive his book I would thank you to mention 

 it favorably in the Journal ; it deserves it fully, for the 

 great accuracy and care with which the facts there con- 

 densed have been gathered. My son, and my old friend 

 Burkhardt, are also with me (upon Sullivan's Island), 

 and look after the large species, so that I shall probably 

 have greatly increased my information upon the fauna 

 of the Atlantic coast by the time I return to Cambridge. 

 In town, where I go three times a week to deliver lectures 

 at the Medical College, and in the evening before a mixed 

 audience, I have my whole female family, so that nothing 

 would be wanting in my happiness if my health was only 

 better. I have heard so little of your own circle, since 

 the Professors Silliman returned from Europe, that I 

 should be delighted to receive a few lines from you, as 

 soon as you can spare me a few moments. What a pity 

 that a man cannot work as much as he would like; or at 

 least accomplish what he aims at! But no doubt it is 

 best it should be so ; there is no harm in being compelled 

 by natural necessities to limit our ambition ; on the con- 

 trary, the better sides of nature are thus not allowed to 

 go to sleep. However, I cannot but regret that I am 

 unable at this time to trace more extensively a subject for 

 which I would have ample opportunities here, the anat- 

 omy of the echinoderms, and also the embryology of 

 the lower animals in general. I regret this the more 

 since I wanted to trace, on a larger scale than I have had 

 an opportunity before, the transformation of intestinal 

 worms, for which it is necessary to have constantly a 

 large supply of specimens on hand. But, however 

 limited my investigations upon this subject are, I have 

 already obtained a very important result. You may re- 

 member a paper I read at the meeting of Cambridge in 

 August, 1849, m which I showed that the embryo which 

 is hatched from the egg of planaria is a genuine polygas- 

 tric animalcule of the genus Paramecium, as now char- 

 acterized by Ehrenberg. You have certainly Steenstrup's 



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