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APLYSIA. 2 1 9 



A. Anterior Aorta. (Unless otherwise stated the branches are 

 unpaired.) 



1. Artery to the Spermatheca. (Fig. 13, spth. a.) This 

 small artery is easily overlooked, but is demonstrated by 

 injection. It arises from the aorta on its left side just as the 

 latter leaves the pericardium, runs along the duct of the 

 vesicle and branches fan wise over the surface of the sperma- 

 theca. 



2. Dorsal Artery. (Fig. 13, dors, a.) This arises from 

 the aorta close to its exit from the pericardium and runs 

 dorsal wards, looping round the retractor muscle of the mantle 

 to supply the mantle and its glands. 



3. Genital Artery (gen. a.). This large artery springs 

 from the right side of the aorta and runs straight backwards 

 dorsal to the branchial nerve (from the parietal ganglion) to 

 supply the genital organs. In some specimens of Aplysia 

 'punctata it gives off one or more branches to the opaline gland, 

 but in others, and in A. depilans, the branch to the gland 

 arises independently from the aorta. The genital artery 

 follows the course of the large hermaphrodite duct in a backward 

 direction and sends branches to it. It then passes through the 

 loop formed by the accessory genital glands, supplying them 

 with blood, and on emerging from the mass runs beside the 

 little hermaphrodite duct, without, as is also the case with 

 the nerve, taking part in the sinuosities of the duct. The 

 artery finally reaches the hermaphrodite gland. 



3 1 . Artery to the opaline gland in specimens where this 

 arises separately from the aorta and not as a branch of the 

 genital artery. 



4. Pedal Arteries (ped. a.). A pair of pedal arteries arise 

 from the aorta at the level of the nerve ring. That on the 

 right is posterior in its origin to that on the left. As already 

 stated the pedal arteries pass backwards ventral to the para- 



