222 THE ACEPHALA. ^ 200. 



Internally, the embryonic halves have three tentacular, stiflF 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."^ 



U Caruf!, loc. cit. Tab. IV. fig. 14. 15 See Rathk^, Cams, and Quatrcfa^es, loc. cit. 



* [End of § 200.] For the embryology of the 1848, p. 531, or in Wiegmami's Arch. 1849, 



Acephala with ahnost a profuseness of detail, see p. 312). This observer has observed with care 



Lovin (Ofversigt af Kongl. Vetenskaps-Acad. the formation of all the organs and their mu- 



Fijrhandlingar, 5« Argangen, 1848, Stockholm, tual embryonic i-elations ; even the resume is too 



1849, or its transl. into German in Mailer's Arch. lengthy to be here quoted. — Ed. 



