262 Summary of current researches relating to 



Incertae Sedis. 



Development of Balanoglossus clavigerus.* — G-ustav Stiasny finds 

 that " Tornaria mulleri " of the Gulf of Trieste is a pelagic stage of 

 Balanoglossus clavigerus, and that the Adriatic " T. krohnii " is a later 

 stage of the same. The ova are liberated within the tubes, and form a 

 layer embedded in mucus. There, or after the eggs have been wafted 

 out by the tide, fertilization occurs. There is a double egg-membrane. 

 The segmentation is total, equal, and radial. A cceloblastula exhibits 

 typical invagination. 



Stiasny distinguishes (1) a period of progressive development, 

 marked by increase in size, in transparence, and in ciliation, and ending 

 in the Tornaria krohnii stage ; (2) a period of retrogressive develop- 

 ment, in which there is decrease in size and transparence and in 

 ciliation ; and (3) the metamorphosis of the pelagic larva into the sand- 

 inhabiting worm. 



The author describes the development of the ciliated wreath, the 

 lobes, the ccelomic pouches, the gill-clefts (as endodermic folds of the 

 enteric wall), and the proboscis-gut (as a diverticulum of the oesophagus). 



Gastrotricha.j — James Murray gives a useful general account of 

 these minute animals, and a bibliography. Most have a roundish, often 

 lobed, head, a more or less distinct neck, a slightly expanded body, 

 diminishing posteriorly to a usually forked, but sometimes undivided 

 extremity. The principal external features are the tubular mouth, 

 certain sensory hairs on the head, various forms of scales and hairs on 

 the dorsal surface, two bands of vibratile cilia along the ventral surface. 

 The animals are on about the same plane as Rotifers for complexity — 

 with alimentary canal, well-developed muscular system, a brain and 

 nervous system, a water-vascular system. They are believed to be 

 hermaphrodite. Most of them occur among the bottom sediment or 

 vegetation in ponds ; at least one species (Chsetonotus marinus) occurs 

 in the sea. They are always in motion, foraging about for food, 

 which they pick daintily here and there. 



Murray gives a key to genera, based mainly on the characters of 

 the furca, and a list of the species recorded. He describes some repre- 

 sentatives of Ichthydium, Lepidoderma, Chsetonotus, and Chaetura. 



Echinoderma. 



Viviparity and Growth in Amphiura squamata.J — A. Djakonov 

 observes that this Ophiuroid must be added to the list of viviparous 

 forms. Numerous young forms of various ages were found in the 

 brood-pouches. During the growth some characters remain constant, 

 especially the mouth-parts, while others, such as the number of arm- 

 spines, the shape of the dorsal arm-plates, and the presence of primary 



* Zool. Anzeig., xlii. (1913) pp. 487-500 (16 figs.). 



t Journ. Quekett Micr. Club, 1913, pp. 211-38 (1 pi.). 



X Zool. Jahrb., xxxvi. (1914) pp. 291-302 (1 pi.). 



