KIDNEY IN RELATION TO WOL?riAN BODY IN THE CHICK. 157 
adjoining the primary tubules, and from an inspection of his 
ficrures it is evident that these cell masses are situated close to 
the Malpighian body of the primary tubule. In the chick I 
have sought in vain for some clear sign in the development 
of these cells which would enable a comparison to be insti- 
tuted with Elasmobranch development. 
In the chick the cells of the Wolffian blastema do not all 
aeem to be used in the formation of the primary tubule. 
Those, that are not, seem to collect at a special point, e. 
just dorsal to that part of the primary tubule which will 
become eventually the Malpighian body. The cells of the 
primary tubule are especially thick at this point, and per- 
haps they give rise to some of the cells for the secondary 
tubule (fig. 11). Even if this is the case — and we may look 
upon the secondary tubule as an outgrowth from the primary 
tubule — it is impossible to say where the secondary tubule 
so formed opens into the Wolffian duct. 
This brings me to another difference between the dorsal 
tubules of the chick and those of Elasmobranchs. In the latter 
they all open into the collecting part of a primary Wolffian 
tubule. In the former they all open independently into the 
Wolffian duct, or it may be into an outgrowth from it, but 
separately from the primary tubule. This latter point I am, 
as above stated, obliged to leave open at present. The 
number of primary tubules present in one segment seem to 
be fairly constant, five or six to each segment, throughout 
the Wolffian body, except quite in front, where there seem 
to be fewer. All segments, from the twentieth to the 
thirtieth inclusive, contain five or six primary tubules. In 
front of the twentieth segment they seem gradually to de- 
crease. In the first segment in -which a fully developed 
tubule appears there seems only to be one, the number 
increasing rapidly to the twentieth. 
The dorsal tubules appear in greater number behind 
than in front. In the twenty-eighth segment I have 
counted as many as four, but more are possibly developed 
later. They correspond in number to the primary tubules, 
i. e. if there are five primary tubules in the twenty-eighth 
segment, there are twenty secondary tubules (five sets of 
four). The most anterior segment in wffiich a secondary 
tubule appears is the twenty-first or twenty-second; I have 
not been able, however, to localise it exactly. 
Develojwient of kidney . — The development of the Wolffian 
blastema from the intermediate cell mass has been described 
as far back as the thirty-fourth segment ; i. e. to the opening 
of the Wolffian duct into the cloaca; it is never seen 
