INTRODUCTION. XI 



IVoliwater Polyzoa), amongst the Ectoprocta, and in the 

 group of the Entoprocta. As this work docs not include 

 the I'hylactolcemata, I shall confine myself at present to 

 an account of the endocyst as it exists amongst the other 

 sections of the class. 



First, then, in the marine Ectoprocta the endocyst 

 appears in the adult cell as a delicate transparent mem- 

 brane, without any cellular structure, a layer of simple 

 protoplasm, lining the ectocyst throughout, and generally 

 lying close upon its inner surface*. But though it occurs 

 in this condition in the older regions of the co3noecium, it 

 is essentially a cellular membrane; and its true nature 

 may be readily determined by the study of the growing 

 extremities of a branch or stolon amongst the Ctenosto- 

 mata (for instance), which offer the greatest facilities for 

 investigations of this kind. Here, according to Joliet, 

 the endocyst appears as a very thick layer, and exhibits a 

 distinctly cellular structure. He describes it as composed 



* I may say here once for all that I do not propose to enter into minute 

 histologieal detail. The space at ray command would not allow of my 

 doing so ; and, apart from this, such detail would be out of place in ;i 

 general sketch like the present. 



On the structure of the endocyst the reader may consult : SMITT. " Oui 

 Hafsbryozoernas Utveckling och Fettkroppar,"(Efv. Kongl. Vet.-Akad. Forh. 

 1865, no. 1, p. 16 ; CLAPARKDE, Zeitachr. f. wiss. Zool. xxi. p. 142; NITSCHE, 

 " Ueb. Flusfra membranacea," Zeitechr. f. wiss. Zool. xxi. Heft 4, pp. 44- 

 46; REICHERT, "Vergleich. anatonmche Untersuchungen iib. Zoobofryon 

 pellucidux (Ehrenb.)," Abhandl. konigl. Ak. d. Wissensch. zu Berlin, 1869, 

 p. 270 ; JOLIKT, ' Bryoz. d. cotes de France,' pp. 56-58, and p. ('>."> ; KUI.KKS, 

 " Hypophorella expansa, ein Beitrag zur Kenntniss der minirenden Bryo- 

 zoen," Abhandl. konigl. Gesellschaft d. WUsenschaften zu Gottingen, xxi. 

 1876, p. 27 (sep.). In the Entoprocfa specially : NITBOIIK, '-Ueb. die 

 Anatomie von Prdicellina echinata" Zeitschr. f. wiss. Zool. xx. Heft 1. 

 p. 18 ; SAJ.EMSKY, " Etudes sur le Bryoz. Entoproctes," Ann. 8c. Nat. se>. 6, 

 Zool. vol. v. art. no. 3; JoLirr, op. cif. p. 01. In tlu> I'hylactolamata: - 

 ALI.MAX, ' E-Veshwater Polyzoa,' p. 1 1 : HVATT, "Observations on Polyzoa, 

 suborder PhylactoUcmata," Proc. Essex Inst. vols. iv. k v. 18T>6-68, p. 26; 

 i, op. fit. |>. ,'.'.! 



