222 



TUE ACEPHALA. 



^200. 



Internally, tlie embryonic halves have three tentacular, stiff points, whose 

 bases arc 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 byssuscs. Subsequently, when the adductor 

 muscle has definitely closed the valves, the embryonic halves are blended 

 together, probably by a new metamorphosis.^^ 



14 Carux, loc. cit. Tab. IV. fig. 14. 



15 See Rathke, Cams, and Quatrefages, loc. cit. 



* [ End of ^ 200.] For the embryology of the 

 Acephala with almost a profuseness of detail, see 

 Lovin (Ofversigt af Kongl. A'etenskaps-Acad. 

 Fijrhandlingar, 5'« Argangen, 1848, Stockholm, 

 1849, or its transl. into German in MiiUer^s Arch. 



1848, p. 531, or in ffieginann's Arch. 1849, 

 p. 312). This observer has observed with care 

 the formation of all the organs and their mu- 

 tual embryonic relations ; even the rtsume is too 

 lengthy to be here quoted. — Ed. 



