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XXXVIII. — On the Anatomy of Leptodora hyalina. 

 By H. E. Forrest. 



{Bead 12th JSfovemher, 1879.) 



Plates XXIV. and XXV. 



Leptodora hyalina is a very interesting Entomostracon, which 

 has only recently been added to the British fauna. It was dis- 

 covered in this country on the 19th July, 1879, in Olton reservoir, 

 near Birmingham, by Mr. J. Levick, who with several fellow- 

 members was on an excursion of the Birmingham Natural History 

 and Microscopical Society. Sir John Lubbock read a paper on it 

 at the meeting of the British Association at Sheffield, and a short 

 description of it is given in the * Midland Naturalist ' for Sep- 

 tember, by Mr. W. Graham. Up to the present time, however, 

 nothing has been published in England upon the anatomy of the 

 animal, and it is hoped that the following remarks may be useful 

 both to those who have seen it, and those who have not had an 

 opportunity of doing so. 



I will describe first its external structure, next the digestive 

 apparatus, then the nervous or sensory organs, and lastly the 

 reproductive organs, and differences between the sexes. 



EXPLANATION OF PLATES XXIV. AND XXV. 



Fig. 1. — Lateral view of male Lcptodora hyalina, to the first abdominal somite. 

 „ 2. — Dorsal view of the entire male animal, a, eye. 6, cerebrum, or brain 

 ganglia, c, antennules. d, commissure, e, cephalostegite, or head shield. /, 

 antennae. ^, 1 to 6, legs. A, upper lip. i, lower lip. j, mandible, k, thorax. 

 /, heart, m, omostegite, thoracic shield, or carapace, n, kidneys, o, 1 to 4, 

 abdomen, p, oesophagus, q, pharynx surrounded by salivary glands, r, stomach. 

 s, rectum, t, anus, u, terminal hooks of the abdomen, v, ligaments, to the 

 ends of which the muscles of the antennas are attached, w, ditto for muscles of 

 the six pair of legs, x, (Esophageal collar, t/, testis. 



Fig. 3.— Antenna viewed from beneath, a, muscles. 6, nerves. 

 „ 4. — Seta from branch of antenna, a, nerve entering from below, and 

 terminating on diaphragm between the joints. 



Fig. 5. — Carapace (omostegite) of female, with ova arranged round it, and 

 showing the opening which fits over the abdomen. 



Fig. 6. — Ideal section of ditto, showing the incurved edges and ovum in situ, 

 one on each side. 



Fig. 7. — Side view of terminal abdominal hooks. 

 „ 8. — Antennule of male, showing the nerve entering from below and 

 traversing the whole length, giving off branches to each of the truncated setaa. 



Fig. 9.— Ditto of female. 

 „ 10. — Mandible, showing teeth on point. 



„ 11. — Head of female, a, outer membrane of eye. 6, crystalline tubes, 

 c, pigment mass, d, muscles of the eye. e, f, right and left ganglia of braiu. 

 g, nerves of the antennules. h, commissure connecting the brain with the thoracic 

 ganglia. », dark oval bodies, j, basal ganglion. 



Fig. 12. — Dorsal view of the heart, showing only the surface muscles. 



