126 FRESHWATER LIFE. 



Eotifera. Occasionally the observer is startled by seeing move across 

 the field of his microscope a thing v^ith long stiff outstretched tail, hke a 

 mouse ; and he can hardly beheve that he is looking at a creature only 

 the 120th of an inch long. It bears the expressive name of Monoccrca 

 rattus, or Rat-single-tail ; the tail being, as already explained, a sort of 

 foot prolonged backwards. This species may be looked for among duck- 

 weed in the eai'Uest days of spring, and all through the summer months. 

 Closely allied to it, if not of tlie same genus, is Mastifjocerca carinata, or 

 Keeled- whip-tail ; whose chief distinction is a dorsal expansion of the 

 integument, hke a keel. The body is about the 160th of an inch long by 

 about the 400th of an inch broad, inclusive of the keel. It has a crimson 

 eye-spot, and is found among confervoid plants. 



I well remember the pleasurable surpi'ise with which I saw 

 for the first time, in the month of May, a fine example of Notommata 

 tigris, so called from having its eye-spots situated on the back of 

 the neck. It raay easily be recognised by its long pair of forceps, 

 or double setae of the tail-foot, the longer blade being the 120th 

 of an inch in length, nearly twice as long as the body. I noticed 

 numerous transverse hues on the thinner half of each seta, about 

 fourteen on the longer, and eight on the shorter of the two. These quasi- 

 jointings evidently contributed to the flexibihty of the organ. The outer 

 cuticle of the body was soft, and allowed the most varied contortions on 

 the part of the animal. On one occasion, in the month of June, I observed 

 in some water taken from a small pond in our Ai-boretum, an egg covered 

 all over with hairs. I watched the egg for some hours in a hve-box. 

 The enclosed animal fidgetted about in its narrow pi-ison, and appeared 

 to be rasping the membrane at one end of the egg. The crimson eye- 

 spot was beautifully distinct. At last the shell was broken thi-ough, and 

 the tiny prisoner struggled into freedom. In a few moments it unfolded 

 its limbs from their doublecl-up posture, and sailed merrily away, unmis- 

 takably a young Scarklium longicauda. As its name, Long-tailed-leaper, 

 implies, the Scai-ii.lium,can leap as well as swim. It leaps with the aid 

 of its tail-foot, which attains the considerable length of the 90th of an 

 inch, the body measuring only the 137th of an inch. 



It is a good plan for the microscopist to make di'awings for future 

 reference of evei-j'thing noticeable which he meets with. Referring to 

 my notebook, I find sketches of the ventral and posterior aspect of wliat 

 I take to bo Euchlanis triquctm, although Pritchard fails to notice the 

 lateral fissure between the upper and lower valves. The body-shield, 

 seen from behind, looks hke a three-cornered hat. It evidently consists 

 of three valves, two dorsal rising in a ridge along the middle and divided 

 by a deep furrow, and one ventral, separated from the foregoing at the 

 sides. There is also a large opening behind, extending some way on the 

 under sui-face, and giving liberty to the tail-foot to double up beneath the 

 ventral valve. My first observed specimen happened to lay an egg while 

 under examination. The egg was the 190th of an inch long, the length 

 of the parent's body being the 80th of an inch, A near relation of 

 Euclilanis is Balpina, a very common object in freshwater gatlierings. 

 The lorica is tlu'cc sided, with a dorsal ridge furrowed from end to end. 



