1911] Michael: Chaetognatha of the San Diego Region. 157 



fathoms, and 39 in open vertical nets below 250 fathoms. None 

 were found on the surface. These data agree that this species 

 is typically mesoplanktonic, that it occurs occasionally above 100 

 fathoms, but not above 25 fathoms. Owing to the small number 

 of specimens obtained any further conclusions are impossible. 



Distrihution of E. subtilis 



Of 50 specimens obtained, two were taken with horizontal 

 closing nets from 160 fathoms, and four from 200 fathoms. The 

 vertical closing nets obtained nine from between 75 and 50 

 fathoms, two between 200 and 150 fathoms, 25 between 250 and 

 200 fathoms, and five between 300 and 250 fathoms. Finally, 

 the open vertical net obtained three in a haul from 250 fathoms 

 to the surface. From these data it is apparent that this species 

 occurs in greatest number between 200 and 250 fathoms. It has 

 never been taken above 50 and rarely above 150 fathoms. We 

 can be sure, therefore, that this species is mesoplanktonic and 

 that its probable center of migration is between 200 and 250 

 fathoms. 



GENERAL SUMMARY AND CONCLUSIONS. 



We have taken ten species of Chaetognatha from the vicinity 

 of San Diego, none of which are new. They are Sagitta hipunc- 

 taia, S. serratodentata, S. lyra, S. hexaptera, S. planktonis, S. 

 enflata, 8. )teglecta, Spadella draco, Eukrohnia hamata, and E. 

 suhtilis. Of these only S. hipunctata was obtained in large 

 enough numbers and frequently enough to permit extensive 

 analysis of its manner of distribution. Concerning it we found : 



1. It is typically epiplanktonic, occurring between the sur- 

 face and 150 fathoms. 



2. It is rarely found below 75 fathoms, and it is most fre- 

 quent and abundant between the surface and 20 fathoms. 



3. Between 6 p.m. and 6 a.m. the species is most abundant 

 above 15 fathoms, while between 6 a.m. and 6 p.m. it is most 

 abundant below 15 fathoms. 



4. The species appears in maximum abundance on the surface 

 and in 4-6 fathoms between 6 and 8 p.m., in 7-12 fathoms between 



