1917-18.] Respiratory Mechanism of the Shore-Crab. 53 
1st being situated under the 1st gill and between it and the base of 
the 6th gill. 
2nd being between the 2nd and 4th gill origins. 
3rd „ 
,, 7 th „ 8th 
4th 
„ 8th „ 9th 
5 ? 
5th „ 
under 
„ 9th gill. 
- r c i6. 
T i-6. 
Fig. 3. — Ventral surface of Carcinus. Branchiostegite and coxte 
of thoracic legs removed on both sides ; third maxillipede 
entirely removed on the left side, on which side the first gill 
has also been removed. 
Sc., scaphognathite ; 1 st—toh i.b., the first to fourth 
“inter-branchial inlets.” Note commencement of flabellum 
of second maxillipede in 2nd i.b. 
Fig. 4. — Oblique view of thorax and abdomen of Carcinus from the 
right side. Carapace and contained organs removed ; also the 
coxse of the thoracic legs. Semi-diagrammatic. 
ls£ /., flabellum of first maxillipede; 3rd commence- 
ment of flabellum of third maxillipede ; ls£ g., first gill ; ls£, 
3rd, iih, and 5 th i.b., the first, third, fourth, and fifth inter- 
branchial inlets. 
X denotes the position, marked by the dotted lines, of the 
“tunnel” formed by the third maxillipede flabellum. 
All excepting the second inlet communicate directly with the adjacent 
inter-coxal spaces. When a probe was introduced through each of the 
latter spaces into the corresponding inter-branchial inlets, it was found 
