46 Leptodora hyalina. 



ON LEPTODOKA HYALINA. 



BY W. P. MARSH.\1,L, C.E. 



[Read before the Society, Novemhev iSth, 1879.] 



This very interesting Entomostracou has attracted special attention 

 from the circumstance that it has been entirely unknown iu 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 Oltou Reservoir and Edgbaston Pool, the 

 only places in this countiy where it has at j)resent 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 iu form and structure that is shown in 

 Leptodora from the ordinary Eutomostraca is of much interest. The 

 most striking difference in its apiDearance from such Eutomostraca as 



EeFERENCES to PL.4.TES IX. AND X. 



a.— Anterior pair of antennae, or antennules. 



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



c— Pair of mandibles. 



d.—Six pairs of limbs, or foot-jaws. 



e.— Labrum, or tipper lip, shown in its raised position by the dotted lines in 



Fig. 5. 

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

 f/.— Compound eye. 

 ?i.— Alimentary canal, or tesophagus. 

 i. — Intestine, or stomach. 

 fc.— Heart. 

 {.— Ovaries. 



?rt.— Oviduct, external opening into incubatmg chamber. 

 71.— Brain. 



o.— Muscles giving rotation to the eye. 

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



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 mcubating chamber. 

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



eggs deposited in the incubating chamber. 

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



heart. 

 Pig. 5.— Side view of the same, 

 yjg. 6. — Pair of mandibles detached. 

 Pig] 7._Eye further enlarged, showing division into two hemispherical eyes, 



muscles giving rotation to the eye, brain, and nerves branching to the 



two antennules. 

 Pig. 8.— Diagram illustrating the construction of the eye. 



