CEUSTACEA 



105 



the appendages, and supply also the parts in their neighbour- 

 hood. 



The arteries divide into smaller arteries or even into arterial 

 capillaries, and these empty their blood into the lacunar spaces 

 or sinuses. The blood finds its way, in the sinuses up the 

 appendages along the dorsal and ventral abdominal sinuses, 

 from the various regions of the cephalothorax, to the large 

 ventral sinus of the thorax. On each side of this sinus, where 



Heart Pericard. si? 



Gitts 



Branchio- 



Extens. abd. 

 miisde 



Testis 



v Dig. gland 

 * Branchiocard. 

 canal 



Intestine 



Flexor abd. 



muscle 



Eff. \branch. 

 Aff. / ves. 



Thar. app. 



Sub-neur. ves. Nerve cord 



FIG. 50. Nephrops. Transverse section through thorax, modified 

 after Parker. 



the pereiopod sinuses open, are a series of apertures leading 

 into the gills by the afferent branchials. These run in each 

 case up the outer side of the column of the gill and into the 

 filaments. The blood is brought back from the filaments by 

 the efferent branchials which run down on the inner side of 

 the column of the gill to open into the branchiocardiac canals. 

 The latter convey the arterial blood up the side of the wall 

 of the thorax to the pericardial sinus. 



Body Cavity. The cavity between ectoderm and endoderm 

 and surrounding the organs is the primary body cavity expanded 

 as a haemocoel. The coelom is present in the embryo as 

 a series of cavities, as in the Annelids, but this mesoderm 



