20 MICROSCOPICAL OBJECTS FOUND 



several forms retractile pseudopodia, — organs of 

 progression projected through pores in the silice- 

 ous cases. If he be correct, this would seem to 

 identify them with the animal kingdom ; but 

 neither have I, nor any of the microscopists with 

 whom I have come in contact, been successful in 

 our search for these pseudopodia. 



A great variety of forms belonging to this 

 interesting group occur in the Levant deposits. 

 From these I have selected some of the most 

 remarkable. Figs. 15 to 21 represent various 

 examples of the genus Navicula. Fig. 15 is a 

 beautiful and not uncommon species, — a exhibits 

 the anterior and b the lateral aspect. Fig. 20 is 

 apparently Ehrenberg's Navicula sigma. 



Fig. 22 is an exquisite species of Surirella, 

 allied to S. elegans, a representing the front, and 

 h one extremity of the shell. Figs. 23 and 24 

 are two species of Cocconeis, a genus of parasitic 

 forms which occur in the greatest abundance on 

 the English coasts, many of the smaller Algae being 

 covered with them in the most incredible profu- 

 sion. Their power of fixing themselves to foreign 

 substances, appears to indicate the existence of 

 something allied to the pseudopodia of Ehrenberg. 



