ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 371 



Morphology of Flustra membranaceo-truncata.* — W. J. Vigelius 

 makes this essay an introduction to a proposed work on the morpho- 

 logy of the marine Bryozoa. The species of Flustra which he has 

 examined offers another proof of the truth of the doctrine that the mode 

 of growth of the Bryozoan stock is of no value as a means of dis- 

 tinguishing the families. The nutrient animal and the avicularium 

 are alone distinctly differentiated individuals ; the brood-capsules 

 are only organs, not individuals. The nutrient animals may be 



(1) budding : these are found on the marginal zone of the colony ; 



(2) perfect : these are the reproductive forms ; (3) resting ; and (4) 

 decaying. The two last are only found near the proximal part of the 

 stock, and are much rarer than the others. The cystid and polypid 

 make up the complete nutrient animal, and in the normal condition 

 consist of integument, nutrient apparatus, and parenchymatous tissue. 

 The author has not been able to convince himself of the existence of 

 a nervous system, but he thinks that its centre is perhaps repre- 

 sented by the small rounded mass of cells, which lies on the 

 anal side of the anterior wall of the pharynx. Like other writers at 

 the present time, the author has made some observations on spermato- 

 genesis, and finds that the spermatoblasts are derived from the repeated 

 division of the spermatospores, but they do not form rounded or oval 

 masses of regularly arranged cells placed on a nutrient blastophore. 

 Vigelius is uncertain whether the explanation of the absence of the 

 blastophore is to be found in the occurrence here of a more primitive 

 condition of things, or in the fact that the surrounding perigastric 

 fluid is highly nutritious. When the spermatoblasts become converted 

 into spermatozoa they are at first pyriform ; the tail then arises at the 

 narrow end, and becomes of some length. 



The histolysis of the digestive tract is described, and the brown 

 body is regarded as having certainly a nutrient function. The view 

 that the cystid and polypid are parts of one and the same individual 

 is supported by the observations of Barrois, the organization of the 

 complete nutrient animal, and the history of the process of germina- 

 tion. The objection that the living cystid appears separately is of 

 little weight, now that Vigelius has shown that the modifications of 

 the cystid are not so numerous as Nitsche supposed — for example, 

 the primitive avicularia are not cystids but polypocystids, the root- 

 filaments are organs, and not individuals, and the same is true of the 

 brood-capsules. As to the objections based on the periodical dis- 

 appearance and subsequent regeneration of the enteric canal, an 

 answer is to be found in the general dictum that morphological facts 

 must not be looked at from a physiological standpoint, as well as in 

 the fact of the wide distribution of the phenomena of regeneration 

 among lower animals. 



The perigastric space is regarded as being a true coelom, but at 

 the same time Vigelius adopts the view of the Brothers Hertwig, 

 that the Polyzoa are pseudo-coelia. 



* Biol. Centralbl., iii. (1884) pp. 70.5-21. 



2 C 2 



