POLYZOA. 



[ 627 ] 



PONTIA. 



orifice, but often from the stem ; these 

 gemmae, on attaining their full development, 

 remain attached to the parent, thus forming 

 the compound organism. In the second, 

 they are formed internally, as buds upon 

 the fimiculus, which is a process passing 

 from the testis to the stomach. Afterwards 

 they become free within the abdominal 

 cavity, from which they escape at an orifice 

 near the disk, according to Beneden, al- 

 though this is denied by Allman. The 

 latter kind, which are often called ova, 

 have an external hard coat, exhibiting the 

 appearance of a marginal ring, and are often 

 of a dark colour ; their development is not 

 dependent upon impregnation, and they 

 seem to correspond to the winter ova of the 

 Entomostraca &c. : Allman proposes the 

 name statoblasts for them. The sexual 

 organs, which usually exist together in the 

 same individual cell, consist of a roundish 

 ovary, attached by a short peduncle near 

 the orifice of the cells ; whilst the testis is 

 a rounded irregular mass attached to the 

 funiculus. The ova, which are first set free 

 in the abdominal cavity, are ciliated and 

 swim freely. 



Four modes of reproduction in the Poly- 

 zoa have been described, three of them 

 taking place in an asexual way : 1. The 

 growth of the whole colony by buds which 

 are external ; 2. The reproduction by eggs 

 formed by internal buds of the endocyst ; 

 3. The production of new polypides and 

 eggs in empty cells (zooecia), by brown 

 bodies which are produced out of the 

 former polypide of the cell by retrogressive 

 metamorphosis j 4. Sexual reproduction by 

 eggs and spermatozoa. 



The Polyzoa are divided into two orders : 



Order I. HIPPOCBEPIA (PhylactoUemata). 



Tentacular disk horse-shoe shaped or bi- 

 lateral; mouth with an epistome; mostly 

 freshwater. 



Order II. INFUNDIBULATA (Gymnolcemata). 



Disk circular, or nearly so ; epistome ab- 

 sent ; mostly marine. 3 suborders : 



Cyclostomata. Cells with a simple round 

 orifice. 



Clieilostomata. Orifices of cells fitted 

 with a thin, membranous or calcareous 

 plate ; with a curved mouth, furnished with 

 a moveable lip. 



Ctenostomata. Orifices surrounded by a 

 circle of setae. 



BIBL. Johnston, Br. Zooph. 253; Busk, 

 Mar. Polyzoa, Brit. Mus. ; Fossil, Pal. Soc. 

 1859; Farre, Phil Tr. 1837; Dumortier 

 and Beneden, Mem. Ac. Brux. 1850 ; Han- 

 cock, Ann. N. H. 1850, v. ; Allman, Freshw. 

 Polyzoa, Ray Soc. ; Gosse, Mar. Zool ii. 1 ; 

 Miiiler, Wieg. Archiv, 1860, 311; Huxley, 

 Invertebr. ; Smitt, Qu. Mic. Jn. 1871, 155 ; 

 Miiiler, Reich, fy D. ReymendSs Ai'chiv, 

 1860; Claparede, Sieb. $ Koll Zeit. 1871, 

 137; Norman, Qu. Mic. Jn. 1868, 212; 

 Hyatt, Pr. Essex Institute, U. S. A. 1868 ; 

 Nitsche, Sieb. $ Koll Zeit. 1870; Barrels, 

 Embryol. 1877 ; Hincks, Polyzoa, 1880. 



POM'PHOLYX, Gosse. A genus of 

 Rotatoria, family Brachionaea. P. compla- 

 planata ; freshwater. (Gosse, Ann. N. H. 

 1851, viii. 203.) 



POMPHOLYX'OPHRYS, Archer, Hy- 

 alolampe, Greef. A genus of freshwater 

 Rhizopoda. 



Char. Rhizopod composed of two distinct 

 sarcode regions, the inner a dense coloured 

 globular sarcode mass, the other colourless, 

 and bearing a number of separate hyaline 

 globular structures ; these are disposed in a 

 layer around the inner globe, which latter 

 gives off slender non-coalescing pseudopodia. 

 BIBL. Archer, Qu. Mic. Jn. 1870, p. 105. 

 PONTEL'LA, Lubb. A genus of Cope- 

 podous Entomostraca. P. Wollastoni, Wey- 

 mouth. (Ann. N. H. 2. xx. 406; Brady. 

 Cop. i. 73.) 



PON'TIA, Fabr. A genus of Lepidopte- 

 rous Insects, of the family Papilionidae. 



This genus contains some of the com- 

 monest butterflies, as P. brassicce, the large 

 cabbage-butterfly ; P. rapa, the small cab- 

 bage-butterfly ; and P. napi, the green- 

 veined white" butterfly. 



The form and structure of certain scales 

 existing upon the under side of the wings 

 of the males are curious ; and the markings 

 were formerly found so difficult to render 

 distinct, that the scales were used as test- 

 objects. 



In the male P. brassicce the upper surface 

 of the anterior wings is free from spots, 

 whilst in the female there are two black 

 spots in that situation. The peculiar scales 

 are represented in PI. 34. fig. 24; fig. 26 

 exhibits a portion of the wing with the 

 ordinary scales. 



In P. rapce and P. napi the anterior wings 

 of the males have a single spot upon the 

 upper surface, whilst there are two upon 

 each wing in the females. The peculiar 

 scales bear considerable resemblance in the 



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