50 REPTILES AND BATRACHIANS. 



lens I could detect the form of the embryo, curled up, but no 

 movements. During that time the eggs had all become detached 

 and solitary with but little of the glair about them ; this latter, 

 which nourishes the egg, having been absorbed. They remained 

 at the bottom of the bowl. When they rise to the surface it 

 may be taken as an indication of their being worthless, as their 

 lightness is due to the gases of decomposition. One must con- 

 clude, therefore, that eggs hatched in four days, as above alluded 

 to, was exceedingly and unusually rapid, and by no means to be 

 expected even in our warmest English springs. Spawn, ordi- 

 narily deposited, is in bulk sufficient to fill a large hen's egg, and 

 the eggs must amount to hundreds. Frogs in captivity and in 

 a warm temperature spawn earlier than in the ponds, and would 

 naturally hatch earlier ; but on one occasion — it was the beginning 

 of July — I had some little frogs, whose tails had only just disap- 

 peared. In an early and warm season they would have become 

 land animals much sooner. 



And now a last glance at the Tunicate tadpole, which we left 

 with a splendid tail to serve it as a swimming organ in the ocean 

 waves. There are several orders of Tunicates, and though the 

 tadpoles may not be precisely the same in all, they are. mostly 

 endowed with the organs already enumerated, and an " auditory 

 vesicle," an " eye-spot of complicated lens-like structure," and 

 actually a brain. Like the frog tadpoles, they also have " suckers," 

 or arm-like projections sprouting from the upper part, with which 

 to anchor themselves to seaweeds or rocks. Would one suppose 

 that such promising little tadpoles could degenerate into plant- 

 like creatures such as those in figs. 2 and 20 ? 



This is the sad tale of what biologists call their degradation. 

 With their suckers they begin a life of laziness. Those arm-like 

 tentacles root them to the spot. No longer using their well- 

 formed tail, it gradually diminishes and finally disappears ; the 

 notochord also, the eye and other partially developed organs 

 share the general retrogression, and the Tunicates remain mere 

 molluscs for the rest- of their lives, with a mouth, a stomach, and 

 very little else. Curious that some kinds should arrange themselves 

 in so symmetrical a manner as those in fig. 21, proving nature's 

 universal tendency to beauty even in " degraded " forms. It is 

 as well to add that their mouth O is provided with cilia, whose 

 constant motion draws in the sea water ; they retain for food the 

 minute animals that swarm in it, and eject the liquid again 

 from the centre orifice, A. Should the cilia draw in anything that 

 is distasteful, or should any injurious substance approach the 

 mouth, it is at once detected and squirted away to a distance. 



