REPORT OF THE DIRECTOR I916 125 



vitality. To cite one example: Schuchert comments on the won- 

 derful vitality of Lingula and Crania. He states Bui. Geol. Soc, 

 vol. 22, 191 1, p. 263) : 



It is also desirable to point out here the wonderful vitality of the living 

 inarticulate braehiopods. Lingula is exposed on the tidal flats of Japan for 

 hours without injury, and on account of its accessibility is regularly gathered 

 by the poorer people for food. At high tide these animals are covered with 3 

 to 4 feet of water. Their habitat may be brackish or foul with decomposing 

 organic matter, even to such an extent that all other shell fish may be killed 

 off, but Lingula will continue to live under such adverse conditions. Yatsu, 

 who has studied living Lingula, tells us that on little estuaries in certain bays 

 of southern Japan their habitats may be covered by sand and mud brought 

 down by stream freshets, so that all of the burrowing shell fish will be 

 destroyed, but Lingula will still live in such stinking places and the 

 individuals tunnel themselves to the surface. The burrows are from 2 to 12 

 inches long, and the movements of the animals up and down in the holes are 

 made by means of the highly contractile and regenerative peduncle. It is 

 thought that Lingula may attain an average of 5 years or even more. Yatsu 

 kept them alive in aquaria with the water fetid, and Morse did the same, 

 keeping his specimens alive for six months in almost unchanged water. 

 Joubin kept Crania, taken from great depths, alive in jars under very adverse 

 conditions for 14 months. In these statements we see the very adverse 

 conditions under which the burrowing Lingula may live, and that the tenacity 

 of endurance is also very great with cemented Crania. In this adaptability 

 lies the probable explanation of why the lingulids and craniids have lived 

 since the Ordovicic. Lingula and Crania have endured all of this vast time 

 apparently without change other than the superficial ones of form, size and 

 ornamentation. 



b Many of the still existing persistent forms are known to pro- 

 duce immense broods, as e. g. Ostrea and Limulus. Of the latter 

 it is told that the quantity of eggs deposited on the sandy shore 

 of New Jersey is so great that scows loaded with supposed shore- 

 sand were found to be filled with Limulus eggs and had to be reemp- 

 tied when the sand became alive ! Also some of our noted relicts 

 are remarkable for the great quantity of the eggs they produce, as, 

 for example, the sturgeon. 



c Further, it is sure that many of the persistent forms are eaters 

 of carrion and refuse and thus being easily fed are able to subsist 

 where other more fastidious types had to leave. The Capulidae, 

 which already in Carboniferous time began to live on the excre- 

 ments of crinoids, and the oyster, exemplify this group. 



Persistence in Species 

 Before attempting a synthesis of the factors obtained by an 

 analysis of the persistence of the genera, we will, in order to 

 obtain a wider view of our problem, briefly survey the persistence 



