18 



BOLIXA ALATA. 



lateral and longitudinal tubes is entirely done away with in subsequent 



changes, as we find that the 

 short ambulacra are the lateral 

 ambulacra, though at first they 

 are more rapid in their growth, 

 but are afterwai'ds outstripped 

 by the ra2)id increase in length 

 of the longitudinal tubes ; but 

 it must be remembered that, 

 in this genus, the fiattening of 

 the spherosome takes place in 

 different planes from Idyia and Pleurobrachia. The young Bolina has 

 now attained a condition m which it will be very easy to recognize 

 the different parts of the adult, it" compared in homologous positions. 

 Fig. 15 is an adult seen from the broad side, corresjjonding to Fig. 12 ; 

 Fig. IG is an adult seen from the narrow side, corresponding to Fig. 



Fig. 17. 



Fig. 16. 



13 ; Fig. 17 is an adult Bolina, seen from the actinal side, corre- 

 sponding to Fig. 14 ; and in Fig. 18 we have the adult seen from the 

 abactinal pole. 



Coast of New England, and northward to the Bay of Fundy (Agassiz). 



Museum diagrams Nos. 1, 2, after L. Agassiz. 



Fig. 14. Fig. 13 seen from the attinal polo, ami more magnified, r, circular tulio ; m, auri- 

 cles. 



Fig. 15. Adult Bolina seen from the broad side, o,/, longitudinal amliula<'ra ; 7, A, lateral 

 ambulacra; 0, eye-speck ; i-7n, digestive cavity; i-o, funnel; v, lateral tube leading to tentacular 

 apparatus just on level of mouth, m ; r, r, auricles ; /, /, prolongation of the longitudinal ambulacra ; 

 n. II, same tubes turning upwards, bending down at x, x; z, z, point of junction of tubes f'roui oppo- 

 site sides ; ?c, prolongation of tubes from the lateral ambulacra. Aliout half natural size. 



Fig. 11). Fig. 1.5 seen from the narrow side, a, h, longitudinal ambulacra; c, li, lateral ambu- 

 lacra ; other lettei-s, as in Fig. l.i. 



Fig. 1 7. Holina seen from the actinal pole ; lettering as above. 



Fig. 18. Bolina seen from the abactinal pole, o, /;, e, /, longitudinal ambulacra; c, d, g, h, 

 lateral ambulacra ; s, *', circumscribed area ; other letters, as above. 



