22 
of the matrix (hypoderm) becomes penetrated by air-canals which independently open at the surface. 
It is true that the air-canals liave walls of chitine secreted by the hypoderm hut 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 ojjening. 
I have carefully examined the dorsal chitinous wall of the gill both as seen from without 
and in sections, but fail to find pore-canals. The author gives a figure of the structures he thus 
designates and I find that his error arose through mistaking veiy 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 articulation 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 net-work of air-holding furrows, since he refers 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 iiortion 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 jireparations excepting as regards the nuclei. In his figure nucleoli are 
represented which I do not find to he present. Further he represents the nuclei as evenly granular 
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 structural feature which I am not 
able to identify in my preparations. He says : 
“Es ist dasselhe nach aussen umgrenzt von einer zarten, doch von Porencanalen durch- 
setzten, daher senkrecht streifigen Cuticula, oben und unten. 
Sodann erscheint die Zellsuhstanz von deutlich streifigem Wesen und starke Vergrosserung 
bei gehciriger Aufmerksamkeit lasst wahrnehmen, dass die Streifen von Liingscanalen oder Liicken 
herrlihren, welche das Protoplasma durchsetzten. Die Zellen von der Flache angesehen zeigen sich 
wie von feinsten, dicht beisammenstehenden Lochelchen 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. 
Armadillidium 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 respLatory tree and grooves present the 
saine characters in both. The only differences are such as relate merely to comparative form 
and size. 
