OF THE ORDER ASCOTHORACICA. 165 



distinctly parasitic mode of life of each species. The Fetrarca bathyactidis of Fowler 

 inhabits the Actiuozoan Bathyactis symmetrica, and lives in the mesenterial chambers 

 of its host. Active powers of locomotion would be useless, and the limbs and tail are 

 merely represented by lobes of the body. The antennas are an exception, ending in 

 two nails and a spine. Yet we find strong resemblances in the enclosing mantle, form 

 of the buccal cone, and general structure to the other genera. 



In the Dendrogaster astericola of Knipowitsch we again have an internal parasite 

 within the body of the Echinoderms Echmaster sarsii and Solaster papposus. What 

 the author draws as figure of the " Larve an slade Oypris " so closely accords in 

 general structure with Laura and Synagoga that it seems impossible to regard it as 

 an immature form. 



Laura gerardice of Lacaze-Duthiers, the most fully described species, has its body 

 covered over by the Gerardia, so that it is protected in a great measure from outside 

 interference, and it is contained in such a gigantic test that were it free it seems 

 impossible that it could lift so large a mass ; moreover, its limbs are free from 

 swimming-setae. 



Synagoga mira is less protected than the preceding genera; it lives externally upon 

 the Antipathes, and instead of being covered by the host it simply clings to it by 

 its massive antennse and would seem to have the power of relaxing its hold and 

 swimming off to attach itself to another part of the host. Its bifid feet are largely 

 furnished with setae, which would enable it to swim easily. 



As compared with Laura, Synagoga shows the following points of difference : — In 

 Laura the mantle which enwi'aps the body is of a prodigious size, in Synagoga it is 

 only large enough just to cover the body. In Laura the antennas are small and 

 insignificant ; in Synagoga they are very large and strong, and the mouth-organs are 

 much more highly and elaborately developed. In Laura Duthiers finds a very small 

 organ which he styles " antennules ou tubercules sous-cephaliques " ; of these I have not 

 been able to find any trace in Synagoga. Laura has only six pairs of unbranched feet, 

 of which the first pair contains the female organ in its upper portion and also discharges 

 the matured ova ; the four following feet have at their bases the organs of the male, 

 and thus the animal is an hermaphrodite. The feet, being without setose adornment, 

 are unfitted for swimming. Synagoga bears the peculiar organ (PI. 34. figs. 8-10) 

 which would seem to discharge at least some of the functions of the first feet of 

 Laura ; behind this are six pairs of bifid feet, which are densely setose, and behind these 

 there are appendages of the first segment of the metasome, which, differing in character 

 in different specimens, are regarded as the distinctive organs of two separate sexes. 

 Lastly, Synagoga has the terminal rami much more fully developed, and, moreover, 

 carries two large spines on the last segment of the metasome above the well- 

 developed rami. 



SECOND SERIES. — ZOOLOGY, VOL. XI. 



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