142 University of California PuMications in Zoology ['Vo'l- 13 



It would be injudicious to attempt to assign causes for the be- 

 havior that is suggested by the preceding facts, but it may be well to 

 point out some of the more general applications that the facts bring 

 up. In the first place, there is reason for thinking that the Schizopoda 

 fall into line with other organisms in the matter of vertical migration. 

 This phenomenon is well marked among the Chaetognatha (Michael, 

 1911), Ostracoda (Fowler, 1909), and Copepoda (Esterly, 1912). It 

 is of interest, therefore, to add to this list the relatively highly organ- 

 ized Schizopoda, though it must be admitted that the evidence regard- 

 ing their movements is not as convincing as that for the other groups. 



In this connection the recent paper of Franz (1913) may be noted. 

 This author gives it as his opinion (p. 271) that it is doubtful if 

 periodic migrations take place. It seems that he must have failed to 

 grasp the evidence brought forward by the investigators jast named. 

 Franz has the notion, as can be seen on page 272 of his article, that 

 this evidence is based upon the relative abundance of the animals in 

 night and day surface hauls. This is not the case, for Michael, Fowler 

 and I have shown that at the times the increase takes place in upper 

 water there is a corresponding decrease in deeper water. If the con- 

 clusion that periodic migrations occur were based only on surface 

 hauls, it might properly be discredited; as it is, however, the weight 

 of evidence favors that view. Furthermore, Franz (1913, p. 272) 

 states that "it seems entirely natural" (to him) that the animals see 

 the nets by day and escape them, but can not do so at night, and this 

 accounts for the difference between the day and night catches. It 

 should be shown, of course, as it has not been, that the organisms 

 actually do escape capture by means of the sense of sight. It is true 

 that the schizopods probably could see the surface nets, and that even 

 the copepods and chaetognaths might, but this criticism certainly has 

 no bearing in the case of some of the ostracods which have no eyes. 



The second general application that may be mentioned is the 

 evident specific hehavior shown in the cases of Euphausia and Nycti- 

 phanes. A similar condition has been noted by Michael (1911, p. 160) 

 for the chaetognaths, and I called attention to it, as shown in the 

 copepods (Esterly, 1912, p. 328). Indications of this occur also 

 among the Ctenophora (Esterly, 1914b, p. 35). 



In concluding this paper it may be well to mention what is known 

 about the occurrence of Thysanoessa and Nematoscelis. Seventeen 

 specimens of the former were obtained in all the hauls, and thirty-nine 

 of the latter (see tables 4 and 5) . 



