Cryptomonadina.] THE INFUSORIA. 107 



right and left side of the creature. The individuals either 

 self-divide simply and completely, or they do not divide at 

 all. " It is possible/' says Ehrenberg, " that the fossil ani- 

 malcules discovered in the flint of chalk and porphyritic 

 formations, and named by me Pyxidicula (see plate xii. 

 upper figures), belong to the genus Trachelomonas." The 

 genera hold the following relations : 



Eye absent -< 



( Form short, self-division ) r 



Lorica obtuse longitudinal or wanting } Cryptomouas. 



and 



smooth I Form long and tortuous ) n , . , 



I Self-division transverse } Ophidomonas. 



Lorica pointed anteriorly Prorocentrum. 



Lorica with a neck and narrow orifice 



Eye present Loricawithtlieorifice ^2^ Cryptoglena. 



without a neck 4 



Lorica a closed box or ) , , , 



V ( pitcher (Urceolus) } Trachelomonas. 



The species of this family are readily recognized by the 

 stiffness or inflexibility they display while swimming, or 

 when brought into contact with other bodies. The lorica 

 of the Prorocentrum and Lagenella is at once perceived 

 to be a distinct covering. When any doubt, however, exists 

 upon this point, a slight degree of pressure in the aquatic 

 live-box, or between two slips of polished glass, will easily 

 determine it. The lorica of the Trachelomonas is of a 

 siliceous quality, and indestructible by fire. 



Genus X. CBYPTOMONAS. The loricated Monads. 

 This genus is essentially characterized (see the Table) by 

 the species being destitute of the visual organ, and having 

 a lorica obtuse, or not attenuated, towards the anterior. 

 Body short, but not filiform; self- division, if any, longi- 

 tudinal. 



