McCluxg.] Microscopic Organisms of Upper Cretaceous. 419 



history. In size they vary from 1-100 of an inch to three inches 

 in their longest diameter, not taking into consideration the 

 problematical Eozoon which covers an area a foot square. In 

 their distribution they are almost omnipresent, being found in 

 nearly every body of water, salt or fresh, and at all depths. 

 Although usually small in size, so numerous have they been in 

 the past that extensive strata of rocks are composed to a great 

 extent of their remains. At present their numbers show little, 

 if any, sign of decrease ; multitudes of them still inhabit the 

 seas, and as they die add their skeletons to the abyssal sediment 

 that represents the strata of rocks now in the process of forma- 

 tion. Over 2000 species have been noted, and of these one-third 

 are now living. Their geological range, so far as known, is 

 from the Silurian to the present time. 



In general the Foraminifera may be described as minute, 

 nucleated, protoplasmic bodies, invested with a shell, through 

 which the body substance, or sarcode, is protruded at one or 

 more points. So far as the living substance, the animal itself, 

 is concerned, there is little difference between the species ; indeed, 

 even between them and their shell-less fellow Rhizopods be- 

 longing to different classes. Motion, limited as it is, and pre- 

 hension are accomplished by the protrusion and retraction of 

 thread-like, anastomosing pseudopodia through the numerous 

 foramina in the shell, or through the mouth opening in the im- 

 perforate forms. Digestion takes place at any point in the 

 body of the animal, and excretion of waste material proceeds 

 merely by the ejection of the undesirable material from any 

 convenient area at the surface. Reproduction occurs by a proc- 

 ess of budding, the resultant individuals being separated off as 

 independent organisms, but more frequently remaining attached 

 to the parent, thus forming the " composite " animal. 



Because of this similarity existing between the living matter 

 of the Foraminifera and the other Rhizopods, no particular in- 

 terest attaches to this part of their organization. It is the 

 shells secreted that are noteworthy. These are remarkable for 

 their great variety and beauty of form. Their structural rela- 



