96 .FRESHWATER LIFE. 



shape can be more or less altered, enabling some species to crawl 

 about like a leecli. Other muscles assist the movements of the ciliated 

 ■wTeath, as well as those of the tail-foot. Under careful illumination I 

 have occasionally observed muscular striae. 



The body-cavity, with its various internal organs, is protected by an 

 integument of greater or less firmness, shaped like a shield, a boat, a 

 spindle, a vase, and so forth. In those cases where the integument is 

 hardest, it may be termed the lorica, corresponding to the carapace of 

 Entomostraca, and having a similar chitinous composition. Its surface 

 is bai-e of ciha, but it is not unfrequently armed with lateral or terminal 

 spines. The only approach to an articulate appendage possessed by 

 Eotifera is that which I have called the tail-foot. It is not a prolonga- 

 tion of the back, and is, therefore, not a true tail. Coming off from the 

 under surface of the body, below the anal orifice, it may be regarded as 

 a kind of foot. It is capable of being shortened, either on the telescopic 

 principle, or, when soft, by contracting in \vi-inkles. The basal portion 

 varies considerably in length, being reduced sometimes to a mere stump. 

 At its narrower end are often inserted, movably, one, two, or three styles, 

 or dagger-hke bristles, which may be very long. When these are two in 

 number, they strongly remind us of a pair of scissors ; when they are 

 three, the middle one is small. With this organ the Rotifera steer them- 

 selves in the act of swimming, or hold on to some support while gi'oping 

 about for food, or even, in a few instances, take veritable leaps. 



With regard to reproduction, the same phenomena of parthenogenesis 

 have been observed, which we noticed when describing the Entomo- 

 straca. The young are born from two very distinct kinds of eggs ; the 

 summer eggs, which are generally, if not always, virgin produce ; and the 

 ■winter eggs, which have been duly fecundated. The latter are preserved 

 against the cold by a peculiar shell, till spring I'etums to hatch them. 

 WTiile the females multiply in enormous numbers, the males are very 

 rarely met with. The latter, moreover, are, as a rule, so unlike the 

 former in appearance, that it is difficult to recognise them as belonging 

 to the same species. It is a curious fact, that in all males the alimentary 

 canal is either absent or rudimentaiy. They are, consequently, short- 

 lived. 



Before briefly considering particular examples of llotifcra, I will here 

 give my authorities for the preceding anatomical sketch, while naming a 

 few works to which the student can refer for a fuller account of the 

 subject. He wiU find that the ablest observers aa-e by no means 

 unanimous on many important points iii the anatomy and life-history of 

 these somewhat puzzling animals. 



Works of reference : — Pritchard's " Infusoria;" Eolleston's " Forms of 

 Animal Life;" Huxley's "Anatomy of the Invertebrated Animals;" 

 Gosse's " Papers in the Philosophical Tz-ansactions." 



'to be COXTINIED." 



