The Microscope. 1£ 



1878), while years ago Prof. Abram Sager described a few facts 

 in the Peninsular Journal of Medicine and allied Sciences. Some 

 of Whitman's results have been challenged and recently Joseph 

 Nossbaum (Z. A. No. 181, p. 609, Nov. 17, 1884), continues the 

 dispute. Whitman describes four pairs of large cells in the de- 

 veloping leech which he calls neuroblasts, supposing that they 

 form the nervous system. Nussbaum says that these so called 

 neuroblasts in reality give rise to what Whitman has called seg- 

 ment cells although he failed to see the connection between the 

 two. As described by Whitman these segment cells give rise 

 to the reproductive organs. The nervous system arises in the 

 way now known to be all but universal in the animal kingdom — 

 by a differentiation from the epiblast. It soon becomes sepa- 

 rated from its parent layer and enveloped in a neurilemma of 

 entodermal origin. The three blood sinuses arise as differenta- 

 tions of the body cavity which is divided into three parts by 

 longitudinal partitions each side of the nervous cord. A curi- 

 ous dorsal organ which disappears with development is also 

 described, the purpose of which seems to be to fasten the em- 

 bryos together. 



The Study of Parasites. — Professor Herbert Osborn of 

 Ames, Iowa, is engaged in the study of the lice found on birds 

 and mammals and would like specimens from all parts of the 

 country and from every species of animal. These lice are far 

 more common than is usually supposed. Almost every species 

 of bird or mammal has 'its peculiar parasites which may be 

 found by looking among the fur or feathers. In birds their 

 favorite place is on the head or neck, for the host is unable to 

 reach these parts with the bill. Specimens may be sent in al- 

 cohol or mounted on slides but each lot shold be labelled with 

 the name of the animal from which they were taken. Under 

 the microscope they are very interesting and beautiful and 

 far from the loathsome animals that lice are usually supposed 

 to be. 



OUTLINES OF EMBRYOLOGY. 



I. INTRODUCTION. 



THERE exist to-day but few more profitable fields for inves- 

 tigation than that presented in the embryology of insects; 

 and since these forms are accessible in all parts of the country, 



