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of tlie matrix (hypoderm) becomes penetrated by air-canals whicli independently open at tlie surface. 

 It is true that tlie air-canals have walls of chitine secreted by the hypoderm but these canals do 

 not open outwards in pores but join one another inwards to form a tree-like cavity which com- 

 municates with the outside of the gill through a single opening. 



I have carefully examined the dorsal chitinous wall of the gill Ijoth as seen from without 

 and in sections, but fall to find pore-canals. The author gives a figure of the structures he thiis 

 designates and I find that his error arose through mistaking very small chitinous hairs for canals 

 lying in the chitinous wall. 



The correllative error in Leydig's account, namely, that then is no opening at the margin 

 of the gill, is made evident by sections (figures 4 and 7). It is true that there is no opening 

 near the articiüation of the gill with the basal Joint but at a point on the opposite margin of the 

 gill. That Leydig was deceived in regard to this becomes understood by the fact that in the 

 species he studied the marginal indentation, indicating the position of the opening, is small and 

 inconspicuous. 



Leydig appars to have observed the uet-work of air-holding furrows, since he i'efers to a 

 portion of the pneumatic part as presenting the appearance of a close net-work ; but he was evidently 

 under the Impression that the net-work was inside the gill and formed a portion of the general 

 pneumatic part. 



The Inner Grills. I find that the figiu-e of a section of the inner gill given by Leydig 

 is applicable to my own preparations excepting as regards the nuclei. In his figure nucleoli are 

 represented which I do not find to be present. Further he represents the nuclei as evenly granulär 

 throughout while I find the chromatin to be situated mainly on the side lying toward the cavity 

 of the gill. 



In his description of the inner gill he mentions one structui-ai feature which I am not 

 able to identify in my preparations. He says: 



"Es ist dasselbe nach aussen umgrenzt von einer zarten, doch von Porencanälen durch- 

 setzten, daher senkrecht streifigen Cuticula, oben und unten. 



Sodann erscheint die Zellsubstanz von deutlich streitigem Wesen und starke Vergrösserung 

 bei gehöriger Aufmerksamkeit lässt wahrnehmen, dass die Streifen von Längscanälen oder Lücken 

 herrühren, welche das Protoplasma diu'chsetzten. Die Zellen von der Fläche angesehen zeigen sich 

 wie von feinsten, dicht beisammenstehenden Löchelchen durchbohrt." 



Contrary to the above I find that the chitine is not penetrated by pores. I find that the 

 protoplasm of the hypoderm is striated, as stated by Leydig, but I do not find that actual canals 

 or lacunae are associated with the Striae. 



Ärmadillidium vulgare Zoddach. 



I have examined the first two pairs of outer gills in this species, both as seen from with- 

 out and in sections, and I find that in all essential features they are identical with the corre- 

 sponding parts in the genera already described. The respiratory tree and grooves present the 

 same characters in both. The only differences are such as relate merely to comparative form 

 and size. 



