ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 991 



anterior end. There are no rods in the ectodermal cells, and the 

 muscular wall is very delicate ; the anteriorly-placed mouth leads 

 into an indistinct pharynx, which is followed by a rudimentary 

 digestive tube. The supra-cesopbageal ganglion gives off on each side 

 two large lateral nerves. The great mass of the body is formed by 

 the genital organs, and their orifice is at the hinder end of the body. 

 Further details as to structure are promised, with illustrations. 



When sexually mature the parasite leaves its host, and secretes a 

 cocoon which coagulates in the sea-water ; this arrangement may 

 perhaps be compared with that described many years ago by Girard 

 iu the American planarian — Planocera elliptica. 



Dinophilus gigas.* — Mr. W. F. N. Weldon describes a new 

 species of Dinophilus from Mount's Bay, near Penzance, which, in 

 addition to other marks of distinction, differs from the species already 

 described by the possession of a well-marked nervous system ; the 

 sexually mature forms are nearly 2 mm. long. The central nervous 

 system is closely attached to the ectoderm, and consists of a brain 

 and a pair of lateral ventral nerve-cords. In the substance of the 

 former the two eyes, each of which consists of one' or two cells 

 loaded with granules of deep-red pigment surmounted by a small 

 cuticular lens, are imbedded. The lateral nerve-cords diminish in size 

 from before backwards, and in the last segment disappear altogether ; 

 no trace of commissures between the cords or of any branches could 

 be found, but the presence of well-developed regions of sense-hairs 

 makes it certain that there is some kind of peripheral nervous plexus. 

 Mr. Weldon does not doubt that when the generative products are 

 mature, the worms rupture their body-wall and die. 



Dinophilus appears to be related to the Archiannelids and to have 

 many features characteristic of the ancestor common to those groups 

 (especially Chsetopods, Gephyrea, Molluscs, Rotifers, and Crustacea), 

 which have a more or less modified trochosphere larva ; the relations 

 of the body-cavity, excretory system, and pharynx point to a 

 Turbellarian origin. 



Spontaneous Division in Fresh-water Planarians.f — With 

 regard to the disputed question of the reproduction of fresh-water 

 Planarians by spontaneous transverse division, Dr. 0. Zacharias states 

 that he has often observed the process in Planaria subtentacnlata. 

 At the commencement of the posterior third of t*he body there 

 appeared a shallow constriction which gradually deepened, while the 

 animal often remained perfectly quiet for several hours. After three or 

 four days it was possible with a magnifying-glass to satisfy oneself of 

 the reality of the division. Separation first took place in the centre, 

 while the sides of the daughter-individual still remained connected 

 with the parent. When the young was completely separated, the head 

 appeared as a small unpigmented process at its anterior end. After 

 twenty-four hours, the eye-spots were apparent, and a new proboscis 

 cavity and a new pharynx were developed. The epithelium of the 

 former is, undoubtedly, of mesodermal origin, a fact which is in 



* Quart, Jomn. Micr. Sci., xxvii. (1886) pp. 109-21 (1 pi.), 

 t Zeitschr. f. Wiss. Zool., xliii. (1S86) pp. 271-5 (4 tigs.). 



