ANIMAL LIFE IN THE GULF STREAM. 



6 59 



ed are seen swimming backward and forward. When looked at 

 through a microscope we see young jelly-fishes, the young of bar- 

 nacles, crabs, and shrimps, besides the adult microscopic species, 

 which are very abundant. The toothless whale finds in these his 

 only food. Bushing through the water, with mouth wide open, 

 by means of his whalebone strainers the minute forms are separated 

 from the water. Swallowing those obtained after a short period 

 of straining, he repeats the operation. The abundance of this 

 kind of life can be judged from the fact that nearly all kinds of 

 whales exist exclusively upon these animals, most of them so small 

 that they are not noticed on the surface. Prominent among the 

 animals obtained from the surface towings is Sapliarina, a small 

 crustacean which is remarkably iridescent, flashing in the sun- 

 light with metallic colors. It darts swiftly about, now green, 

 now blue, and very conspicuous on account of its ever-changing 

 hues. Another similar form is red. At all times, and in nearly 

 all places, both in the Gulf Stream and in the warmer waters out- 

 side, there is an interesting transparent animal called Salpa. At 

 first glance it would appear 

 to be structureless, but, if 

 carefully studied, a mouth, 

 a stomach, and other organs 

 will be found, which place 

 it among the higher inver- 

 tebrate animals. They swim 

 around in large schools, but 

 on account of their great 

 transparency are scarcely 

 visible. Whether or not 

 they serve as food for other animals I do not know, but it seems 

 that a meal made of them would be rather unsatisfactory on ac- 

 count of the great quantity of salt water that enters into their con- 

 struction. They often have a curious blue parasite inside the body 

 walls, and this is about the only visible sign of structure. Very few 

 animals are free from parasites, and in the fishes they are numer- 

 ous, burrowing into the gills, in the roof of the mouth, and all over 

 the external portions of the body. On sharks we sometimes find 

 them four inches long, an inch of which extends into the flesh. 

 There is one called Penella, which is very long, and has a hairy tuft 

 on the outer end. In most cases this parasite has attached to the 

 external stem a species of barnacle, which itself has small parasites. 

 Parasitic tendencies degenerate an animal, so that many of the 

 once essential organs become useless and are lost. We see this 

 well illustrated in Penella, which is an ally to the shrimp, but has 

 so changed, by losing its feet and other organs, as to bear but little 

 resemblance to these higher crustaceans. Degeneration is still 



Fig. 9.— Doliolum (an Ascidian allied to the 

 Salpa), 



