398 PRINCIPLES OF ANIMAL BIOLOGY 



Porpoise ij)or' pus). An aquatic mammal closely allied to the whales and dolphins. 



Poterioceras (po te' ri os' er as). A genus of extinct cephalopods of the gomphoceran 

 type. 



Precocial (pre ko' shal). Able to run about as soon as hatched; said of certain birds. 



Precoracoid (pre ko' ra koid). A ventrally situated bone or cartilage of the pec- 

 toral girdle in Amphibia and some reptiles. 



Primary (pri' ma ri). For application to spermatocytes, see spermatocyte. F(jr 

 application to o6cji;es, see oocyte. 



Primate (pri' mate). A mammal of the order including man and the ape-like animals. 



Priority, Law of (pri or' i ti). The rule that the name first given a species along with 



a description is the one that shall be accepted when different names have been 



applied to the same species. 



Proboscis (pro bos' sis). The trunk of an elephant, consisting of the elongated nose 

 and upper hp. Also a fleshy projection of other sorts. 



Proccelous (pro see' lus) . Having the anterior end of the centrum concave, the 

 posterior end convex ; said of vertebrae. 



Procyon (pro' si on). The genus of Carnivora to which the raccoon belongs. 



Proglottis (pro glot' tis) (pi., proglottides, pro glot' ti deez) . One of the individuals 

 in a chain of a tapeworm. 



Pronuba (pro nu' ha). A genus of moths some members of which feed on Yucca seeds. 

 Prophase (pro' faze). Any early stage of mitotic cell division, prior to the splitting 

 of the chromosomes. 



Prosecretin (pro' se kre' tin). A substance in the walls of the small intestine from 

 which secretin is produced. 



Prostomium (pro sto' mi um) . A rounded projection overhanging the mouth of an 

 earthworm. 



Protandrous (pro tan' drus). Maturing the male germ cells before the female cells; 

 said of an hermaphrodite. 



Protein (pro' te in). One of many organic substances, compounds of amino-acids, 

 which therefore contain carbon, hydrogen, nitrogen and oxj^geu and often other 

 elements. The molecules are large and very complex. Lean meat and egg 

 albumen contain quantities of proteins. 



Proteocephalus (pro' te o sef a lus). A genus of tapeworms. 



Proteolytic (jrro' te o lit' ik). Protein-splitting. 



Proteose (pro' te ose). Any one of a number of substances, derived from the hydrolj'sis 

 of proteins, which may be precipitated from solution with ammonium sulphate. 



Proterozoic (pro' ter o zo' ik). Belonging to the era preceding the Paleozoic. 



Proteus (pro' te us). A genus of salamanders. 



Protogynous (pro ioj' i nus). Maturing the female germ cells before the male; said of 



hermaphrodites. 

 Protonema (pro' to ne' ma). A thread-like growth originating from a spore of certain 



plants, as the mosses, and from which arise the leafy sexual siioots. 

 Protonephridium (pro' tone f rid' ium). A primitive excretory organ consisting of 



flame cells and connecting tubes. 

 Protophyta (pro' toji' la). One-celled plants. 

 Protoplasm (pro' to plaz'm). The living matter of which animals and plants are 



essentially composed. 



