ZOOLOGY AND BOTANY, MICROSCOPY, I 47 



Copepod fauna is distinct from that of the Arctic seas, and that the 

 species which are typical of this region, and most numerous, do no! 

 extend far into the southern Atlantic. 



New Parasitic Copepod.* — V. Dogiel describes Entobius loimice 

 g.etsp.n., an cndoparasitic Copepod in the intestine of a Terebellid 

 {Loimia medusa ?). The female, 3-5-4 mm. in length, shows a head- 

 region (with reduced appendages, two pairs of antenna, mandibles, a 

 pair of maxilla?, and a pair of maxillipedes) ; a thoracic region of four 

 segments bearing biramose appendages of great simplicity ; and a pos- 

 terior region without appendages. The male is cpiite like the female, 

 but smaller. The first larval stage is a metanauplius. As to the 

 systematic position of this interesting form, it may be referred to the 

 vicinity of Mytilicola intestinalis. 



Nerves of Entomostraca.f — Alfred Fischel has been able to dis- 

 cover, by intra-vitam staining with alizarin, some new details regarding 

 the nervous system in Daphnia hngispina (e.g. a network on the posterior 

 and ventral wall of the brood-capsule) and Bosmiva Irmijicornis (e.g. a 

 ganglion at the root of the caudal setae). 



Optic Organs of Eucalanus.J — C. 0. Esterley has studied the 

 light-recipient organs of the Copepod, Eucalanus elongatus. The median 

 eye is of the tripartite type ; each lateral ocellus consists of two basal 

 plates and of nine retinal cells ; the ventral ocellus contains ten cells, 

 and is provided with a single basal plate similar to those of the lateral 

 portions of the eye. The basal plates are products of the retinal cells, 

 and probably do not contain the pigment of the eye, which is believed 

 to be in a central cell, upon or in which the three divisions of the 

 eye rest. The tapetum lies upon the peripheral margins of the central cell. 



The retinal cells are provided, in their cytoplasm, with " interior 

 bodies " or phaosomes, generally of a flattened rod-like form, arranged 

 in such a way that w T hen sectioned the long axis of their section 

 corresponds with the long axis of the section of the cell. The axis 

 cylinders of the optic nerves leave the retinal cells at the basal or deep 

 ends (those adjoining the pigment-cell), and pass through, or to one 

 side of the basal plates to enter the central cell. The individual fibres 

 traverse the central cell toward the brain. There are twenty-eight fi 1 in is in 

 the optic nerves, the same number as the sum of retinal cells. Probably 

 one fibre comes from each cell. 



The terminations of the nerves in the sensory cells are not in the 

 form of a " Stiftchensaum." The neurofibrils are rather irregular, 

 somewhat beaded and branched ; each ends in a club-shaped enlarge- 

 ment. Consequently the character of the nerve-ending cannot be 

 regarded as similar to that in the visual cells of worms, as Eesse has 

 maintained. 



The cells of the median eye are not of the inverted type commonly 

 found among flat worms and Polychtets. Therefore the median ey< 

 not to be regarded on this character as a structure inherited from worm- 



* Zool. Anzeig., xxxiii. (1903) pp. 561-7 (5 figs.). 



t Tom. cit., pp. 698-701. 



X Bull. Mus. Oomp. Zool. Harvard, liii. (1903) pp. 1-55 (6 pis.), 



