LEPTODORA HYALINA. 257 



ON LEPTODORA HYALINA.* 



BY W. P. MARSHALL, C.E. 



This very interesting Entomostracon has attracted special attention 

 from the circumstance that it has been entirely unknown in this country 

 until the present year, having been previously found only on the 

 Continent ; but it has now been found in great abundance in the neigh- 

 bourhood of Birmingham, at Olton Reservoir and Edgbaston Pool, the 

 only places in this country where it has at present been met with. This 

 little creature is also interesting from its remarkable transparency, which 

 renders the internal structure unusually clear for examination ; but this 

 transparency and the absence of colour cause the object to be easily 

 overlooked, notwithstanding its comparatively large size, extending to 

 one-third of an inch in length. The circumstance of its not having been 

 found here before may be partly due to this cause, as well as to the 

 unusual depth below the surface of the water, four feet or more, at 

 which it is found. 



Fig. 1, Plate IX., is a drawing of the male Leptodora ; and Fig. 2 the 

 female, showing the eggs in the ovary. Fig. 3, drawn to a larger scale, 

 shows the eggs in the external incubating chamber. 



The singular modification in form and structure that is shown in 

 Leptodora from the ordinary Entomostraca is of much interest. The 

 most striking difference in its appearance from such Entomostraca as 



Refeeences to Plates IX. and X. 



a. — Anterior pair of antennae, or antennules. 



b.— Posterior pair of antennae, or swimming arms. 



c— Pair of mandibles. 



d. — Six pairs of limbs, or foot-jaws. 



e— Labrum, or upper lip, shown in its raised position bv the dotted lines in 



Fig. 5. 

 /.—Carapace, forming the incubating.chamber in female. 

 g. — Compound eye. 

 h.— Alimentary canal, or rasophagus. 

 i.— Intestine, or stomach, 

 fc.— Heart. 

 I.— Ovaries. 



m.— Oviduct, external opening into incubating chamber. 

 n.— Brain. 



o.— Muscles giving rotation to the eye. 

 p.— Pair of nerve cords from the brain to ganglia situated above the month. 



Fig. 1.— Male Leptodora, partly ventral view, showing the eye, brain, heart 



alimentary canal, and stomach. 

 Fig. 2.— Female Leptodora, partly dorsal view, showing the two ovaries, external 



opening of oviduct, and incubating chamber. 

 Fig. 3.— Enlarged view of female showing mandible and mouth, and showing 



eggs deposited in the ii cubaiing chamber. 

 Fig. 4.— Front view of mouth, further enlarged, showing pair of mandible3 and 



hare. 

 Fig. 5.— Side view of the same. 

 Fig. 0.— Pair of mandibles detached. 

 Fig. 7.— Eye further enlarged, showing division into two hemispherical eyes 



mnscles eiving rotation to the eye, brain, and nerves branching to the' 



two antennules. 

 Fig. 8.— Liagram illustrating the construction of the eye. 



* Bead before the Birmingham Natural History and Microscopical Sociefcv 

 November 18th, 1879. y ' 



00 



