41 



a new order was created for its reception as well as the 

 reception of Hexartura polyptra, another extraordinary- 

 rotifer found in Egypt in 1853, but never seen since. This 

 new rotifer, named by Hudson Pedalion mirum, resembled 

 in its general conformation the Namplius larva of one of the 

 freshwater Entomostraca. Not only did it possess, in 

 common with other rotifera, a ciliary wreath on its bead, by 

 the movements of which it was driven through the water in a 

 manner somewhat similar to that of the screw of a steamship, 

 but it had in addition six limbs, which enabled it to skip several 

 times its own length. Here then we have in Pedalion the 

 connecting link between the two sub-kingdoms, Vermes and 

 Arthropoda. 



Eor a long time England was Pedalion's only home. But 

 it has since been found in several others parts of the world. 

 I myself have come across it in China, the waters of which 

 literally swarm with beautiful microscopic organisms, and also 

 in the desolate volcanic island of Ascension in the middle of 

 the Atlantic Ocean. 



Now a second species of this wonderful genus has been 

 discovered, mounted specimens of which are now under the 

 microscopes on the table. 



The differences between the two species are soon told. In 

 •size they are nearly equal, viz., about -j-i-g- inch in length, 

 though I think that the new P. fennicum is rather broader 

 than P. mirum. If you will glance at the sketches of these 

 two rotifera, you will see (marked a) two peculiar stylate 

 processes projecting from the posterior end of the body of 

 P. mirum ; these are absent in P. fennicum. Taking into 

 consideration the six limbs, the ventral limb (mark 6) is seen 

 to project considerably beyond the hinder end of the body in 

 P. mirum, whilst in the new species it only just reaches 

 beyond the posterior end, and is therefore considerably 

 shorter. There is also a marked difference in the Literal 

 limbs. In P. mirum, the dorso-lateral limb (g) is consider- 

 ably smaller than the ventro-lateral limb (j), whilst in P. 

 .fennicum, the two lateral appendages are nearly equal in 

 size. The bristled extremities of all the limbs, but especially 

 the ventral limbs, are more expanded in P. mirum than in P. 

 fennicum. 



Such are the main differences. The internal anatomy, as 

 far as is known (the digestive, nervous, water vascular, 

 reproductive, and muscular systems), is similar in both 

 species. Only females have been found at present, many of 

 them bearing one or two reddish eggs attached to the hinder 

 part of the body. 



