516 PROCEEDTXas OF THE NATIONAL MUSEUM. vol. xxviii. 



around inward and meet on the median line beneath the intestine. 

 The o-cneral course of these main currents is the same, but the details 

 ditler oreatly. As Pickering" and Dana well say, they "are merely 

 main directions, and the blood flows into them or from them throuoh 

 all their extent/" The points where the main currents ])reak up into 

 smallei" currents and the courses of the latter also vary gireatly. Pick- 

 ering and Dana describe in Calujux <-iii'fiis two points upon the median 

 line where there is a valvular action, functioning somewhat as a hinirt 

 in this circulation. 



One of these is situated at the apex of the posterior thoracic joint; 

 there are here three valves, one in the center ventrally and one on 

 either side dorsallv, the dorsal and ventral valves opening alternatel3\ 

 The pulsations are regular, and from ;^)0 to 4(» a minute. The second 

 point is between the l)asal joints of the second antennw. (Pickering and 

 Dana call them the flrst maxillipeds.) Here there is a single meml)ra- 

 nous valve playing back and forth and thus preventing the return of 

 the blood that has passed it in either direction. 



It must not be inferred that these two descriptions are characteristic 

 of the two genera and that C'a//'(/us species have the valves while 

 Zrjjr(j/?/it/u'ir(is species do not. This would not l)e true; the descrip- 

 tions merely serve to indicate the amount of diversity to ))e found in 

 the details of circulation. 



After examining a larger number of species while alive it may be 

 found advantageous to puljlish these details in a future paper. 



RESPIRATION. 



There are no independent organs of respiration, Init Hartog, in ISSO, 

 descril)ed the anal respiration in C'l/r/ojts, (_'((iiiJiocaiiq>tu><^ 'An(\. allied 

 genera, and suggested that the blood of these parasites may l)e aerated 

 in the same wav. That this is the actual condition the present author 

 has proved in several instances. And iii'st, as noted l)_v A. Scott (lUOl, 

 p. 21), the chitin exoskeleton is so tliick over nearly all the l)ody that 

 verv little aeration could be efl'ected through it, while the endoderm 

 lining the rectum is thin enough for this purpose. 



Then there are the necessary nuiscles for such respiration, dilators 

 running from the abdomen wall to the rectum, wliile the peristaltic 

 movements, common to the rectum as to the rest of the alimentary 

 canal, serve for the contraction. These dilator muscles are figured by 

 Clans (18G1) for Lrj)e<ip]ifJn irus fJi<>)iips<)n! (which he calls ('(iJi(/ns 

 l>r(()icJu(iI!s) in Plate XXXIII, tig. T) of his memoir. They are said to 

 be present in Lepcoplithe'ii'us pectoral is by A. Scott (1901, p. 21), and 

 they have l)een observed by the present author in LepeophtJieirni< 

 edvardsl and in Cidhpix luipox (tig. 28) and C. Ixmito. These facts 

 create a strong })resumption in favor of the existence of such resjiira- 

 tion, and it was onh' left to actually observe it in the living animal. 



