LOXOSOMA. 367 



posterior extremity of the body, and consists of a highly retrac- 

 tile nipple-shaped body, bearing a few stiff setse on its summit. 

 It can be withdrawn, so as to become almost invisible. 



As to the developmental phases which connect the gastrula 

 with this curious larva, they are perfectly simple, and it may be 

 said that the rough draft, both of the form and of the different 

 parts of the larva exists already in the gastrula, and that it is 

 merely by successive differentiation of the rudimental elements 

 that the perfect embryo is constituted. 



The author has been unable to trace the later stages in the 

 history of the embryo, or to determine the precise mode in which 

 it is transformed into the perfect animal. He has observed occa- 

 sionally on the skin of the Phascolosomas club-shaped bodies, 

 composed of a thin cuticuiar envelope, filled with very trans- 

 parent protoplasm containing refractive granules, which were 

 attached by the smaller extremity and completely closed above. 

 He is inclined to believe, though quite unable to speak with any 

 certainty on the point, that these bodies may enter into the series 

 of transformations ; that the embryo, after becoming attached, 

 may be enclosed by a thick cuticle, and undergo a complete 

 dissolution of the tissues, such as has been observed in other 

 Bryozoan larvae, and that finally within the elongated cyst formed 

 by the cuticuiar envelope a polypide may be developed by 

 budding. After careful and prolonged examination, however, no 

 distinct traces of any such process have been determined. 



On the other hand, the analogy supplied by the study of the 

 larva of Pedicellina affords no support whatever to this view.^ 

 In the latter the internal organs are most fully developed as they 

 exist in the adult ; even the rudiments of the reproductive organs 

 and of the brood-chamber are distinguishable. It is difficult to 

 imagine that all these organs thus definitely constituted are to 

 disappear that a new and similar set may be evolved, and it is 

 therefore probable that the larva of Pedicellina undergoes no 

 dissolution of its tissues, but passes into the perfect animal 

 through the loss of the ciliary organs and the development of .a 

 tentacular corona and a stem. Is it likely, then, that such being 

 the course of development in Pedicellina, the kindred Loxosoma 

 passes through a totally different cycle of ontogenetic phases ? 



In the absence of conclusive facts the Author leaves the question 

 for future decision.^ 



1 It would surely have been nearer the mark to say that the case of Pedi- 

 cellina affords a very strong presumption against any such supposition. — 

 Transl. 



- The author has somewhat underrated the amount of our knowledge 

 respecting the larval history of Pedicellina. So long ago as 1845, Van 

 Beneden, in his ' Recherches sur les Bryozoaires,' described the larva of 

 his P. Belgica, and gave a very interesting account of some of the later 



