326 University of California Publications in Zoology {|Vou.9 
the oscillations of a confined swarm is without foundation, con- 
sidering the length of time and the area over which our observa- 
tions extend (Fowler, 1909, p. 304). Damas et Kofoed note 
(1905, p. 410) conditions among the copepoda, similar to those 
observed here. 
Franz (1911b, p. 10) states that it is doubtful if vertical 
migration occurs regularly; the catches may be larger at night 
because the animals can not see the nets and are taken in larger 
numbers than during the day when the nets are visible. He 
says that if nets are constructed that tend to prevent the escape 
of the organisms the difference between the day and night catches 
diminishes. 
The possibility that the animals see the nets and avoid them 
during the day should not be ignored, but it can not apply in 
the case of such organisms as the Halocypridae among the 
Ostracoda, which have no eyes (Fowler, 1909, p. 302). The fact 
of diurnal migrations is so well established for the Chaetognatha 
(Michael, 1911) and Copepoda of this region, and the Ostracoda 
of the Biseayan region (Fowler, 1909) that it is needless to more 
than mention those instances to indicate the extent to which such 
movements appear to occur. 
Franz also (1911b, pp. 8 and 9) states, on the basis of his 
experimental work, that we may assume that copepods in their 
natural surroundings do not react phototactically, and he uses 
this, apparently, as an argument against the occurrence of 
diurnal migrations. On the contrary, he says the movements 
observed in nature take place because of unrest for short periods. 
Furthermore, he claims (p. 12) that his laboratory experiments 
have shown for a number of animals (among them certain pelagic 
copepods) that movements toward or away from a source of 
light do not take place because of unequal illumination, but 
because of the unusual and abnormal stimulation produced 
when the animals are put into the vessel. 
Tn another paper this author states his views concisely (Franz, 
1911a, p. 10), where he says: ‘‘Wenn die freibeweglichen Tiere 
beim Laboratoriumsversuch phototaktisch reagiren, so tun sie 
fiir eine etwas liingere Zeitsdauer das, was im Freileben das 
Fliehen vor ungiinstigen Einflussen oder das Aufsuchen geeig- 
neterer Aufenthalts ist. Die Lichtsverhiltnisse sind fiir die 
