ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



227 



knowledge of Polygordius, Fraipont defines the genus as follows, in 

 contrast to Protodrilus. 



Archiannelids, relatively large. 

 Mouth non-protrusible. 

 King of pre-anal papillae. 



Small size. 



Muscular protractile pharynx. 



Two lateral posterior fixing lobes. 



Ventral longitudinal furrow. 



Cilia in furrow, in the vibratile pits on 



the tentacles, and as rings on each 



segment. 



Two parallel and separate fibrillar nerve- 

 cords. 



Very mobile tentacles with vascular 

 branches. 



Movements Turbellarian-like. 



Generally hermaphrodite. 



No metamorphosis. 



Protodrilus purpireus Schneider; P. 

 flavocapitatus Uljanin; P. schneideri 

 Langerhans ; P. Icuckartii Hatscbek. 



Cilia in adult only in vibratile pits, and 

 round the mouth. 



Exceptionally scattered tufts of cilia. 

 Unpaired, median ventral nerve-cord. 



Tentacles with one axial nerve-bundle. 



Vermiform movements. 



Separate sexes. 



Development with metamorphosis. 



Polygordius lacteus Schneider ; P. apogon 

 M'Intosh ; P. villoti Perrier ; P. cry- 

 ihrophihalmus Giard ; P. neapolitanus 

 Fraipont ; P. appendiculatus Fraipont. 



IV. Habitat. — Prof. Fraipont then describes the habitat and mode 

 of life of Polygordius, their sandy or fine gravel haunts, their contractile 

 movements, their habit of fixing themselves by their posterior end, their 

 great brittleness, their nutrition, sometimes apparently worm-like, in other 

 cases discriminative. The females are usually larger than the males, 

 they are (in some species) destroyed by their reproduction. The free 

 surface life of the larvae, their love for light when it is essential to their 

 life, their nutrition of small pelagic animals, are then described. 



V. Geographical distribution. — Polygordius has only been found as 

 yet in European seas, at least in its adult state. Their occurrence in 

 the North Sea, the Mediterranean, &c, is noted. 



VI. General conclusions. — Professor Fraipont gives a welcome 

 resume of the various opinions held in regard to the position of Poly- 

 gordius, and the morphological import of its larva. Believing it to be 

 in the strict sense an Archiannelid, he discusses its relations with 

 Ophelida3, with Protodrilus, with Histriodrilus, and with Dinopliilus. 

 After a thorough discussion of the views held in regard to the larva, 

 and an appreciation of the merits of each and all ; after opposing 

 especially the theory of Hatschek, Balfour, and Kleinenberg, who regard 

 the larval characters as ancestral, to that of Lang and Sedgwick, who 

 regard them as adaptive, Fraipont is forced to conclude in the cautious 

 statement^ that in the actual state of our knowledge, it is not yet 

 possible to determine the morphological import of the larva of Poly- 

 gordius or the trochosphere of Annelids, nor to draw from it any certain 

 conclusions as to the phylogeny of the Annelida. 



j3. Nemathelminthes. 



Spermatogenesis in Chaetognatha.* — M. A. Bolles Lee has investi- 

 gated the spermatogenesis of Sagitta. After some preliminary historical 

 matter he proceeds to describe his results, which are thus (in abbreviated 

 form) summarized. 



As Hertwig has shown, the testes arise from the same primordial 



* La Cellule, iv., n.d., pp. 107-33 (2 pis.). 



