52 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The blastomeres have at first but little coherence, yet the reciprocal 

 position of the first cells is typical. At first there is no apparent plan 

 of symmetry, but later on there is bilaterality. In the first blastomeres 

 the nuclei are tabulated, but as the cells become smaller the nuclei are 

 " regulated," though there may be considerable diversity of size even in 

 the same embryo. There seems to be an epibole resulting in a solid 

 mass, but it is impossible to distinguish germinal layers. Around the 

 ellipsoidal solid mass there is differentiated an enveloping layer of flat 

 cells. 



As to organogenesis, the solid mass which forms the larva gives rise 

 to (ectodermic) bulb, cerebral ganglion, sense-organs, and hooks, and to 

 the (endodermic) wall of the gut, and to presumably mesodermic elements 

 occupying the rest of the space. The gut arises from a hollowing 

 (creusement) of the solid rudiment ; its primitive dorsal orifice is different 

 from the definitive ventral orifice ; there is at first a complete tube as in 

 Hirudinea. Complications in the gut appear later, but in the larva, as 

 in the adult, there are glands annexed to the pharynx. There is an 

 anterior hint of a coelomic cavity, primarily in communication with the 

 gut. The hooks have a twofold origin,— (a) a deep part arises in a sort 

 of follicle, (6) the superficial part is cuticnlar. The cuticle arises from 

 a complete investment whose cells go further and further apart, remaining 

 connected by a delicate membrane. Among the cells some are differen- 

 tiated into ciliated elements with particular localisation. 



Fish Parasites.* — Dr. Edwin Linton gives a list of fish parasites 

 from the Woods Holl region, with their hosts. A number of forms are 

 described, amongst which are twelve new species, seven of which belong 

 to the genus Distomum. Some notes on certain pathological conditions 

 in the hosts are also given. 



The same author f gives an annotated list of the parasites of Woods 

 Holl fishes which have been previously described by him in various 

 papers. Analytical keys for the determination of genera of Cestodes 

 and species of Distomes mentioned in the paper — and there is a goodly 

 list — are added. Notes on the food of the fishes examined for Entozoa 

 are also given. 



Incertee Sedis 



Development of Phoronis ijimai. | — Iwaji Ikeda finds that this 

 species occurs abundantly in shallow water near the Misaki Marine 

 Biological Station, and breeds from about November to May or June. 

 The eggs and early embryos occur in embryonal masses attached to the 

 lophophore of the adult, while four kinds of Actinotrocha larvae were 

 found in the surface waters of the inlets near the station. The abund- 

 ance of the materia], especially as regards early stages, enabled the 

 author to make some observations on fertilisation and segmentation. He 

 finds that in Ph. ijimai, the oogonia fall into the body-cavity by the de- 

 hiscence of the ovarian wall, and develop there until they reach the 

 state of primary oocytes. They then travel gradually upwards to the 

 region of the nephridia, and finally leave the body by these and are 



* U.S. Fish Commission Bulletin, 1S99, pp. 2G7-304. 



t Tom. cit., pp. 405-92. 



t Journ. Coll. Sci. Tokyo, xiii. (1901) pp. 507-92 (6 pis.). 



