28: 



PHYSIOLOGY OF THE INVERTEBRATA. 



Carapace 

 Chelje 



Ambulatory limbs 

 Abdominal \ 



segments 



Outer struc-' 

 ture weight , 



Inner struc- 1 

 ture weight | 



Total. 



817 

 1 184 



736 

 ( 156 

 1 63 



2956 



103 



Chitin. 



Lime 

 carbonate. 



150-32 



236.80 



147.20 



31.20 



12.60 



587.12 



55.00 



656.80 

 933.00 



579-97 



122.93 



49.64 



2342.34 



66.98 



Lime 



phos- 

 pliatc. 



9.87 

 14.20 

 8.83 

 1.87 

 0.76 



35-52 



rereentage. 



OUTER. 

 Chitin . 20.00 



CaCOj 

 Ca,P.,0„ 



. 78.80 



1.20 



100.00 



1.02 



INNER. 



Chitin . 34.00 



Teeth (iQandibles) 



Stomachical teeth 



ter) weighed 



weighed . 17 grains, 

 (horny mat- 

 • • • 27 )) 



CaCOj 



Ca3P,0, 



65.00 

 1. 00 



100.00 



The nutritive fluid (blood) of an edible crab weighing 

 about 8000 e-rains contained : — 



Calcium phosphate 

 Phosphoric acid 



1 1. 10 grains 

 15-78 „ 



Having alluded to the secretion of the shells and exo- 

 skeletons in the Mollusca and Crustacea, we now proceed to 

 describe the organ of Bojanus in Anodonta cygnea and other 

 Lamdlihrancliiata. The function of this organ has been 

 investigated by Mr. Harold Follows, F.O.S., and the author.* 

 It is a paired, elongated, oval, glandular sac with folded walls. 

 It is situated beneath and behind the pericardium, and in 

 front of the posterior adductor muscle (see Fig. 18). This 

 organ is composed of a yellowish or brownish spongy tissue, 

 which is covered with a closely ciliated cellular layer. Its 

 secretion is acid to litmus paper, and it contains uric acid, 

 urea, and calcium phosphate. The presence of these com- 

 pounds were proved by the methods already described in 

 this chapter. 



* Chemical News, vol. 51, p. 241 ; Journal of Chemical Society, 1885, p. 921 ; 

 Proceedings of Royal Society of Edinhuryh, vol. 14, p. 233. 



