40 SUMMARY OF CURRENT RESEARCHES RELATING TO 



shows five arm-rudiments in crescentic series. There is an interval 

 (aboral brachiolarian Qotch) between the antero-dorsal and antero- 

 ventral arm-rudiments (rudiments ir and [). Ciliation persists from the 



blastula stage onwards. Imt becomes lessened over the general surface. 

 The ciliated hands are locomotor except the transverse portion of the 

 preoral hand. The special adoral ciliation consists of the peristomal 

 ring- and oesophageal loop, and acts towards the stomach except on ;i 

 small segment of the peristomal ring. The surface between the preoral 

 and postoral hands is a food-gathering area ; the buccal cavity and the 

 first part of the oesophagus can be emptied by a backward flexion of the 

 preoral lobe. 



The author describes the internal structure of the larva, and the 

 process of metamorphosis in its external and internal aspects, and directs 

 attention to the following conclusions of morphological or general 

 interest : — 



The presence of a rudimentary posterior enteroceelic outgrowth 

 suggests a principle which goes far to reconcile or explain what seemed 

 extremely divergent modes of origin of the enterocceles in starfish and 

 Echinoderms, and in Enteropneusts. 



There is morphological equivalence between the epigastric i larval 

 right posterior) coelom and the hypogastric (larval left posterior) coelom. 

 In the early larva there is a right middle ccelomic region morphologically 

 equivalent to the region on the left side which gives rise to the 

 hydroccele, viz. the left middle ccelomic region. No rudiments of the 

 right hydroccelic region are recognizable after normal metamorphosis. 



The separation of the young starfish from its stalk, and certain 

 other considerations, harmonize with the view that the asterid and the 

 crinoid stalks are morphologically equivalent. The dorsal sac is an 

 " epicardial " pulsating sac homologous with the pericardium of Balano- 

 glossus. There is detailed morphological and probably also functional 

 correspondence between the haemal systems of Asterids and Enteropneusts. 

 In particular, the axial organ and pharyngeal coelom of Axteria* are 

 homologous respectively with the left pharyngeal vessel and the left 

 pharyngeal coelom of Balanoglossus. A bilateral " starfish " can result 

 from the metamorphosis of a double-hydrocosle brachiolaria. 



The rays of a starfish should be numbered according to a scheme 

 which makes the anal inter-radius in part the most anterior and in part 

 the most posterior of the inter-radii. There is evidence of the existence 

 in the late larva? of a sub-epidermal nervous network and of a system 

 of n euro-muscular fibres. Of all Echinoderm larvae the brachiolarian 

 type has probably retained the greatest numb : of primitive characters 

 and acquired the smallest number of secondaiy characters. New data 

 are given regarding a number of points relating to adult structure and 

 function, e.g. regions and curvature of the alimentary canal, the structure 

 and function of the madreporite, the hamial system, the ccelomic and 

 perihaemal ciliation, etc. 



Studies on Holothuroids.* — Joseph Pearson proposes a re-classifica- 

 tion of genera MiiUeria and ffolothuria, which have been separated by 



* Spolia Zeylauica, ix. (1914) pp. 163-72 (1 pi.). 



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