154 HALF AN HOUR WITH SEA-MATS AND SQUIRTS. 



over stones, &c. Every now and then the zigzag 

 thread expands into a little cup, variously coloured, 

 which is the true ascidian. In many respects 

 Lepralia seems allied to the sea-mats, and its stony 

 scurf may be seen covering seaweeds. When ex- 

 amined with magnifying glass, it is a very beautiful 

 object. But, perhaps the most curious of all, is that 



Fig. 81. 



Botryllus polycyclas. 



known as the Salpa, in which we have the principal 

 of alternation of generation carried out, very fully. 

 The first discoverer of this peculiarity, Chamisso, was 

 ridiculed and laughed at when he made it known to 

 the world. But " they laugh most who win," and 

 Chamisso's discovery has since been abundantly 

 verified. In the words of that naturalist, " a salpa 

 mother does not resemble her own daughter or 



