19(Ht] MICROSCOPICAL JOURNAL. 321 



CDiitiibution lo liie ;etiology of human malaria. It also is 

 indicated that Ross's discoveries are sugcrested by, and 

 are confirmatory of, Grassi's previous results. 



Role of Insects, etc., as Carriers of Disease. — For 

 the following summaries we are indebted to the Journal 

 of the R.M.S. Dr. G. H. F. Nuttall, in the Johns Hop- 

 kins Hospital Report VIII., 1899 (see also Lancet, Sep- 

 tember 16th, 1899), makes a timely and valuable contri- 

 bution to the literature of animal and vegetable parasites, 

 and their definitive and intermediary hosts. This occurs 

 in a critical and historical study of the part played by in- 

 sects, arachnids, and myriopods as carriers of bacterial 

 and parasitic diseases of man and other animals. Among 

 the more important and interesting features of the essay 

 may be mentioned the evidence adduced to establish the 

 connection between flies and the spread of cholera, ty- 

 phoid and plague; the association of Texas or tick fever 

 with Ixodes bovis, tsetse-fly disease with Glossinia mor- 

 sitans and its recent visit to an infected animal, the sub- 

 ject of filariosis, and the mosquito-malaria theory. The 

 bibliographical appendix is extensive. 



Regeneration in Earthworms. — A. P. Hazen has made 

 some interesting experiments. It has been shown by 

 Spallanzani, Morgan, and Hescheler that a short piece cut 

 from the anterior end of an earthworm dies without re- 

 generating the posterior end, although such a piece often 

 lives for several weeks, or even months. It was not known, 

 however, whether, if such pieces could be kept alive for 

 a long time, they would regenerate ; or whether, if re- 

 generation did occur, a head or a tail would develop. By 

 grafting in a reversed direction the small anterior end of 

 one worm upon a large posterior piece of another worm, 

 the small piece can be kept alive for a much longer time. 

 The results showed that a head may regenerate from the 

 posterior end of the seventh segment if it is kept alive for 

 some months by grafting. It seems, comparing this with 



