G1 
On the Anal Respiration of the Copepoda/’ by Makcus 
M. Hartog, MA., B.Sc., F.L.S. 
In a note on Cyclops read at the British Association I 
pointed out that its respiration was exclusively anal. I 
have now made out the same in Canthocamptus (fam. Har- 
pacticidce), and Diaptomus (fam. Calanidce). In all three 
the mechanism is the same; at regular intervals, after 
the backward sway of the intestine, the anal valves 
open for an instant and then close, giving just time for 
a slight indraught of water after the opening, a slight 
expulsion at the close. The necessary pressure to con- 
fine the animal seems to interfere somewhat with these 
movements, sometimes stopping them if excessive ; hence I 
refrain from noting with illusory exactness the intervals 
between each respiratory movement. 
It is to be noticed that the rectum contains as a rule 
liquid only, the bolus of faeces remaining in it but a short 
time. By endosmose the liquid in the rectum will tend to 
be at the same condition of gaseous saturation as the body 
fluid around it, kept constantly agitated by the backwards 
and forwards sway of the stomach. During the short inter- 
val that the anus is open an approach to gaseous equilibrium 
with the external water takes place, even despite the very 
slight movement of the water (shown by the little change 
of place undergone by suspended indigo or carmine particles). 
In the absence of any other suitable respiratory apparatus, 
no one can hesitate as to the function of the action I have 
described. 
In the Nauplius larvae of Cyclops and Diaptomus the 
working is slightly different. The rectum is a subspherical 
muscular sac, which at regular intervals contracts so as to 
leave a linear cavity (along the long axis of the animal), 
and immediately dilates, sucking up the water from 
without 
