248 EVENINGS AT THE MICROSCOPE. 



not protruded from the front ; their whole interior edges 

 come into contact. The mallei are simple, slender bent 

 rods, apparently without distinct articulation. During life 

 they are thick and irregular in outline, owing to their 

 being invested with dense muscles ; as is the whole upper 

 portion of the mastax. These muscles conceal or disguise 

 the form and action of the parts during life, but the intro- 

 duction of a drop of solution of potash into the water in- 

 stantly dissolves away the fleshy parts, leaving the solid 

 organs, or those composed of chitine, beautifully clear, 

 and fit for observation. Without this aid it would be im- 

 possible to resolve the structure of these minute animals. 



The little Sword-bearer, like the Brachionus, carries its 

 eggs attached to the hinder part of its body, for some time 

 after they are discharged ; the minute green oval bodies 

 that you see sticking to the side of this specimen, are not, 

 however, eggs, but parasitic animalcules (Colacium vesicu- 

 losum), which very frequently infest this species, adhering 

 to various points of the shell, and even to the sword-fins. 



What I have now to submit for your examination is one 

 of the rarest species of the class, and certainly not the 

 least singular in its form. It is the tripod Wheel-bearer 

 (Actinurus Neptunius). When fully extended, its length 

 exceeds that of almost every other species, for it reaches 

 about one-twentieth of an inch ; but its extreme thread-like 

 slenderness precludes the unassisted eye from taking cog- 

 nizance of it, as its thickness, even when greatest, is not 

 more than one six-hundredth of an inch. 



From this excessive length and tenuity, the appearance 

 of the creature is very remarkable. It may be likened to 

 a cylindrical tube, out of which protrude a great number 

 of draw- tubes from both extremities, principally the pos- 

 terior one. Those in front terminate in an oval proboscis, 

 which having a sort of finger at its extremity, and two 

 eyes, with an antennal tube projecting obliquely back- 

 wards, presents, when viewed laterally, a strong resem- 



