ROTIFERS. 



247 



rotary organ, cilia, or eye, and it has a tail-like foot with two conical and short segments at the end. 

 The mastax differs from that of the ordinary kinds, and is very complicated. The animal is about 

 5? T th of an inch in length. Another and smaller species (Taphroeampa annulosa) has a fusiform annulose 

 body with a forked tail, and there is no rotary organ. Moreover, the genus Balatro, which lives 

 upon the surface of Oligochete Worms, has neither rotary organs nor eyes, and the tail is bilobed. 

 Several genera, such as Cheetonotus, Ichthydium, and Dasydites, have no mastax, nor eyes, 

 nor trochal discs ; but the Ixxly is furnished with bristle-like hairs, downy hairs, and cilia 

 on the ventral surface ; usually there are two tail-like processes. They are minute, and are 

 from -^jtli to yiyth of an inch in length, and would appear not to be Infusoria, but 

 really Rotifera, allying the class to the Tvu-bellarian Worms. 



The first family of the Rotifera is that of the Philodinidse, and they are free-swimming 

 forms, which can also creep like Leeches, the ends of the body being alternately fixed and 

 loosened. They have two wheel-like rotary organs, and the body is somewhat spindle- 

 shaped, and very contractile, so that it can be formed into a globose shape, and the 

 powers of extension are considerable. The tail end or foot is jointed like the slides of 

 a telescope. The genus Rotifer belongs to this family, and the common Wheel Animalcule 

 is Rotifer vulyaris. It has a white fusiform body -o^th to ^jth of an inch long, gradually 

 narrowed to the foot which has two horn-like toes. The anterior part of the body has a 

 proboscis ciliated at the end, and the two eyes are placed there. The wheels are two in 

 number, are round, and placed at the sides of the front part of the body. MONOLA- 



Rotifer citrinus has a yellow body, and Rotifer tardus has tlie body deeply constricted C1LIS 

 into segments. 



The genus Philodina has the two eyes on the region below the extreme end, and in general 

 appearance the species greatly resemble Rotifer. Some are rose red in colour, and the ova when 

 deposited are red. The ova are deposited in little heaps, and the parent remains in their neighbour- 

 hood, and even looks after the young. 



A common species* has two frontal red eyes, and at the tail end there are two horny processes 

 and three terminal points or toes. They are large, being from T yth to -^th of an inch long, and 

 are common. In the genus Monolabis there are no horn-like processes. 



The other Philodiniclse have no eyes, and in the genus Callidina the horn-like 

 processes on the foot are present, there being six, and there is a proboscis. This 

 proboscis, like that of most other Rotifers, appears to be an entry and exit for 

 water, and it certainly is used in locomotion. One of the genus is parasitic on Crus- 

 tacea, such as Gammarus and Asellus. One of the Rotifers found in Egypt has 

 neither eyes, nor proboscis, nor horn-like processes on the foot, and the rotary organs 

 are placed at the ends of processes on the front of the body. Another Egyptian 

 form (Typhlina viridis) is simpler than the last mentioned, and has no processes 

 for its rotary discs. Probably both of these Rotifers are young Philodinge. 



The second family, the Brachionidee, have a broad body more or less enclosed 

 in a shell, or lorica. The foot is composed of short segments, and the rotary 

 organ may be double or of three median and two lateral parts, these last only 

 being rotary organs, the cilia of the others remaining extended without motion 

 during the action of the other. 



The lorica, or shell, is thick in this family, so much so as to prevent the internal organs 

 being readily seen. The genus Brachionus has an eye on the neck, and the foot is forked. The 

 mastax is very visible, and the crushing pieces are terminated by finger-looking ends made up 

 of the same kind of hard skin or chitine that forms the lorica. which has projections on it fore 

 and aft on either side. 



The species are numerous, and the individuals also, and they are about -^th to T Vth of an inch 

 in length. One of the genera of the family differs from the last in having no forked toot, and the 

 lorica is striated or has facets on it. Some of these ^nursea, however, have plain shells, but in 

 most there are fixed or movable spines on its edges. Some of the family have two eyes, and one 



* Actinurns neptinmis. 



BRACHIONUS AM- 

 PHICEROS. 



