222 THE ACEPHALA. $ 200. 
Internally, the embryonic halves have three tentacular, stiff points, whose 
bases are surrounded by collars. 
Near the hinge a large muscle passes from one valve to the other ; this, 
from convulsive contractions which occur from time to time, gradually 
approximates the valves, which are wide open when the young individual 
escapes from the egg. These valves are trigonal and slightly convex. One 
of their sides goes to form the hinge, while the two remaining, which are 
a little arched, unite at an angle opposite. With this angle is articulated 
a prolongation curved downwards and inwards, and whose convex side has 
several spines.” After their escape from the eggs, these embryos are held 
together by their entangled byssuses. Subsequently, when the adductor 
muscle has definitely closed the valves, the embryonic halves are blended 
together, probably by a new metamorphosis.* 
i Carus, loc. cit. Tab. IV. fig. 14. 15 See Rathké, Carus, and Quatrefages, loc. cit. 
* [End of § 200.) For the embryology of the 1848, p. 531, or in Wiegmann’s Arch. 1849, 
Acephala with almost a profuseness of detail, see p. 312). This observer has observed with care 
Loven (Ofversigt af Kongl. Vetenskaps-Acad. the formation of all the organs and their mu- 
Worhandlingar, 5 Argangen, 1848, Stockholm, tual embryonic relations; even the résumé is too 
18489, or its transl. into German in Miiller’s Arch. lengthy to be here quoted. — Ep. 
