304 TROCEEDINGS OF THE ACADEMY OF [May, 



ill certain cells strongly differentiated and old, such as those with 

 which we are dealing, there exist fibres without connections, nothing 

 would stand in the way of admitting that certain trabeculre break 

 their bonds and are isolated," etc.(/. c, p. 158). The apparent 

 connection of fibres with reticulum is due to bad fixation. Sub- 

 limate-acetic, Hermann's, usually Fleraming's, and a number of 

 other much trusted fluids produce a similar effect ; but it is not the 

 picture one gets in the fresh cell, the structure of Avhich is not 

 difhcult to determine. 



The alveoles measure on the averagee 2,« in diamter in all ages- 

 Between them in the fresh cell is a substance in which I have not 

 been able Avith a t5 immersion to recognize granules or any other 

 formed elements. Granules do appear at times about the nucleus, 

 but these have no part in the ground structure. With nearly all 

 fixations, except possibly alcohol and formo -alcohol, the homogeneous 

 interalveolar substance precipitates in the form of fine granules 

 visible with the immersion lens. 



h. Nucleus. 



aa. Form. — The nucleus of the " mid-gut" cells has been the 

 object of several investigations within the period of modern tech- 

 nique. In 1885 Carnoy probably mistook some unnatural forms 

 of the nucleus for stages of amitosis. In 1887 v. Bambeke de- 

 scribed many of these unnatural forms in the " mid-gut " cells of 

 Oniscus and other isopods, which may be produced artificially. His 

 method was to examine the intestine in blood of the animals, either 

 with or without the addition of methyl green. For permanent 

 preparations he fixed in osmic acid, stained with methyl green, and 

 mounted in glycerine. He recognized clearly that the irregular 

 forms, frequently found in such preparations, were due to some 

 mechanical disturbance. 



Ziegler and vom Rath, like Carnoy, doubtless erred in supposing 

 the elongated nuclei to be in process of division. Ryder and Pen- 

 nington, overlooking v. Bambeke' s paper, described elongated 

 nuclei stretching from one cell to another as a form of non-sexual 

 conjugation of nuclei. All subsequent writers have recognized that 

 for the most part these deformations are due to mechanical causes 

 incident to preparation of the intestine for study. Schimkewitsch 

 (20), in calling attention to this error, says: " Bei Bearbeitung 



