22 2 



3. Planula (Gastrnla). 



4. Actinula, with twelve primitive tentacles. 



5. Adult actinia or polype. 



IV. THE CTENOPHORiE. 

 These beautiful animals derive their name Ctenophorse, or 

 "comb-bearers," from the vertical rows of comb-like paddles, situ- 

 ated on horizontal bands of muscles, which serve as locomotive 

 organs, the body not contracting and dilating as in the true jelly 



than any animals of which we have yet spoken, a3 it has been 

 shown by the two Agassizs that they have a true digestive cavity, 

 passing through the body cavity, with a posterior outlet, and orig- 

 inating in the same manner as in the Echinoderms. From this 

 alimentary canal are sent off chymiferous tubes which " correspond 

 in every respect with the water tubes of the Echinoderms" (A. 

 Agassiz). The rows of paddles are intimately connected with the 

 chymiferous tubes, so that the movements of the body are in di- 

 rect relation with the act of breathing. Moreover these animals, 

 while in the disposition of the organs following the radiate plan 

 of structure, are also more truly bilateral than any of the lower 

 classes of radiates. The sexes are united in the same individual ; 

 the ovaries in Idyia are on one side of the main chymiferous tube, 

 and the spermaries on the other, both being brilliantly colored. 



Referring the reader for farther details to Mr. A. Agassiz's "Sea 

 Side Studies," where these animals are described and illustrated 

 with sufficient detail for the general reader, we will now turn to 

 their mode of growth, under the guidance of the same author, 

 whose recent richly illustrated memoir, with others by Kowalevsky 

 and Fol leaves but few gaps to be filled by future observers. 



Development. Agassiz states that the Ctenophoree are readily 

 kept in confinement, and from twelve to twenty-four hours after 

 they are captured lay their eggs, either singly or in strings, or, 

 as in Idyia, in a thick slimy mass. The CtenophoraJ of our 

 eastern coast spawn from late in July through August and Sep- 

 tember. "The young brood developed during the fall, comes to 



