386 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



w 



a 



pairs of bcemal bundles of setae, and as many neural booklets are developed 

 very early ; tbere is tben a pause before tbe otber cbsetopodia appear. 

 Tbe autbor discusses tbe results of earlier observers, and is largely in 

 agreement witb Claparede and Eisig. We bave as yet no observations 

 on tbe permanent chsetopodia of tbe Hermellidse. Tbe term of tboracio 

 or ventral shields is applied to tbe more or less distinctly bounded 

 integumentary tbickenings, wbicb appear on tbe lower surface of these 



vporms, between tbe lateral rows of 



Q parapodia. Tbey are characterized by 



jg ^5, :S :2 their intimate connection with a large 



rS ' 8^ ^ ■cu q number of unicellular glandular tubes 



which open to tbe exterior between 

 their cells and project for a variable 

 distance into the coelom ; the arrange- 

 ment, form, and structure of tbese are 

 somewhat fully discussed, as is also 

 their development. 



Tbe eighth chapter is occupied by 

 an account of the cephalic gills of tbe 

 Serpulaceae, and tbe oral tentacles of 

 the Hermellidge ; tbe ninth deals with 

 tbe mouth, which, in both tbese groups, 

 is terminal in position ; the changes 

 undergone during the larval stages are 

 described. The frontal tentacles form 

 tbe subject of tbe tenth chapter ; tbey 

 are paired, are often greatly reduced, 

 or may be altogether wanting ; so 

 hidden are tbey that no observer but 

 Pruvot has as yet detected them ; they 

 are hollow filaments, which are pro- 

 vided externally on their median upper 

 surface with a special ciliated epi- 

 thelium ; tbey bave a proper muscular 

 layer, and are lined internally by tbe 

 peritoneum ; below tbe ciliated longi- 

 tudinal grooves there runs, in the 

 hypodermis, a nerve which comes from 

 the brain ; and in the axial cavity is a 

 much coiled contractile vessel which 

 ends blindly in front. 



Tbe central nervous system is very 

 fully described ; the ventral medulla 

 of the two groups under consideration 

 is characterized by consisting of two 

 separate halves or cords ; in each segment there are two pairs of ganglia 

 connected by two pairs of transverse commissures ; with tbese two pairs 

 of primary nerves correspond. The development of this system is also 

 discussed very fully. 



The vascular system forms tbe subject of tbe twelfth chapter, and 

 tbe peritoneal glands that of tbe thirteenth ; tbe latter are the gonads, 

 tbe sites of origin of tbe lymphoid cells, and the pigmented lymph- 

 glands or cbloragogue-glands. 



Serpulacese 



Spiouid stein-form 



Free-living (carnivorous) ancestor 



