GUSTAV EISEN: P0NT0SC01 I 



In another paper on this genus 1 will return to a review of this and its 



relationship with other species, but at present 1 will online myself to the pecul 

 which have been found so far only in Pontoscolex, in the equatorial i mite. 



The first one to describe these cell- was Edmond Perrier in 1872. In his beautifully 

 illustrated monograph on Urochaeta he figures these cells as unicellular glands. Yi 1 

 dovsky, who probably never himself saw the Pontoscolex cells, compares them to 

 the bristle cells in Anachaeta, which view has lately been adopted by B d. An- 



other author, one of our most careful observers, Dr. R. Horst, who has had an oppor- 

 tunity to investigate this subject closer, considers these cells as ol a nature, 

 and in no way resembling the bristle cells in Anachaeta. The figure given by Dr. 

 Horst of one of the cells is in the main correct, but, as it appears ui low 

 power, Dr. Horst himself recognizes that the liner structure of il idermis- 

 bodies is not sufficiently known. It is this gap in our knowledge of them that 1 

 am now endeavoring to fill. 



The material on which my investigations have been made was collei 

 by myself in Mexico. The worms were slowly killed by dropping 1 ubli- 



mate-alcohol in water, and when dead they were extended on a glass plate, t 

 for some minutes in saturated corrosive sublimate in alcohol of 95" 0, and then pre- 

 served in simple alcohol of the above strength. Afterwards they were paraii 

 sectioned, and stained on the slide, and mounted in gum-thus in xylol. The section- 

 varied in thickness from 2?, p. to 8 ;j. and were mostly cross-sections of the hod 

 I soon found that longitudinal sections were rarely useful; as only a few of the central 

 sections could be strictly vertical to the cell. For staining I tried the whole scale 

 of anilines, etc., but found only a few of them to answer. Hematoxylins gave poor 

 results, and so did carmines. The following were the most useful: Eosin, watery, 

 with 5°/o glycerin; after-staining with watery thionin. Orange G. watery. 25 with 

 3o°,'o alcohol, after-staining with thionin. Iron-alum-haematoxylin-method of R. I 

 denheim gave, take it all in all, the most detailed images, while gold-chloride and 

 hydrochloric acid gave very useful ones. The lower cytoplasmic floor of the cell 

 stained best by Congo-red in watery solution, but only slightly in eosin. 



Location Of the cells. Previous investigators have already shown that 

 the cells in question are found in the equatorial of each somite, in a line with the 

 bristles. I find that the cells are present in every somite, including the clitellar 

 ones, where they are quite numerous. In the caudal zone they are never s< 

 but both anteriorly and posteriorly of it I always found them. In the most an- 

 terior somites- i, ii and iii - the cells are scarce; in the prostomium 1 never found 

 them. Instead of being situated in a single row as described by Perkier from the 



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