192 DESCBIPTION OF {^Polygasfrica. 



on the creature. The double xoroboscis is used as an organ of hico- 

 motion, and the bright red eye affords the usual evidence of the 

 existence of a system of sensation. Self-division in the transverse 

 direction, somewhat modified, has been observed to take place. 



CnxoEOGONiuM euchlorum. — Body spindle-shaped, very pointed at 

 both extremities ; tail short; coloiu' sparkling green. The eye of this 

 animalcule, although distinctly marked, is, nevertheless, so delicate, 

 that it may be easily overlooked ; but when the creature is dried upon 

 a plate of very clear glass, both the eye and the double proboscis are 

 readily seen, and may be weU preserved as a permanent microscopic 

 object. Group 79 represents six creatures in one cluster, each with its 

 double proboscis ; above them is one about to divide into tlii'ee ; and 

 on the right of this are three young animalcules. Found in water- 

 butts, &c. : on ponds it forms the green matter of Priestley. Length 

 1-llOth to l-280th, exclusive of the tail. 



It was in this species that M. Weisse thought he had discovered a 

 fonn of propagation analagous to that by ova. He observed the 

 contained green matter, with its scattered vesicles, contract in some 

 measure upon itself, exhibit a constriction, indicating a line of di\'i- 

 sion, subsequently followed by the appeai'ance of other constrictions, 

 until the entire contents assumed a nodular form, resembling a bimch 

 of grapes. This grape-bunch mass possessed a certain degree of 

 movement within the enclosing integument, and as the process of 

 development further proceeded, its separate particles or granules 

 also displayed a movement among themselves, increasing in vigour 

 until the outer envelope burst and gave them exit as so many distinct 

 independent beings, moving freely about in the surrounding water. 



These young forms so produced, especially in their aggregate state 

 before discharge, resemble JJvella Bodo, and M. Weisse thinks Chlo- 

 rogonium euchlorum, and Glenornorum tingem, but other stages of their 

 development. From the above observation, that naturahst is led to 

 the conclusion that Pohjgastrica do reproduce, in some sort, by ova, 

 and that some forms described by Ehrenberg as indej^cndent genera, 

 are but different phases of development of the same being. 



Genus CoLAcruM. The friends ? of the Water Flea. — This genus is 

 characteiizcd by the creatures belonging to it being endowed with a 

 BJugU) eye, and attaching themselves to other bodies by means of a 



