8 NATURAL HISTORY BULLETIN. 



latter, and seem to have a definite object in climbing over the 

 sides and into the interior of hydrothecae and gonangia. 

 There is no evidence that they are able to repair damaged 

 parts. 



4. An examination of living sarcostyles, under a high 

 magnification, disclosed certain cells on the distal surface 

 which had the characteristic outlines and movements of 

 amoeboid cells, and contained foreign particles. 



It would seem from the foregoing observations that the 

 sarcostyles of P. ftimiata are primarily neither fighting per- 

 sons, nor persons concerned in the repair of mutilated or 

 diseased parts. It is probable, on the other hand, that they 

 do remove extraneous matter, or dead organic material from 

 the interior of the hydrothecae 1 and gonangia, and that they 

 may aid in the capture and ingestion of food for the colony. 



Origin of the sex-cells. This species is an excellent one 

 for the demonstration of the ccenosarcal origin of the sex-cells 

 in the Plumularidce as first announced by Weismann. 2 The 

 gonangia are so excessively numerous that a single series of 

 sections may often be obtained which will show nearly all 

 stages of this interesting process. The course of events in 

 P. pinnata agrees very closely with Weismann's description 

 of the origin of the sex-cells in P. cchinulata, both ova and 

 spermatoblasts, arising in the endoderm of the stem and after- 

 wards migrating into the gonophores, ultimately appearing as 

 ova, or sperm-masses in the matured structures. The ova 

 breakthrough the "stutzlamella" and are fertilized and under- 

 go segmentation between the stutzlamella and the ectoderm. 

 Although the ultimate division of the spermatoblasts may 

 take place in the ectoderm, the primary divisions occur in the 

 endoderm. I have been unable to find any cells recognisable 

 as spermatoblasts in the ectoderm, although very satisfactory 

 serial sections were made of the male gonophores. It may 

 be, however, that my specimens were too near maturity to 



1 E. Metschnikoff, Quart. Jour. Alter. Sci. No. 93. 



8 See Die Entttehnng der Sexiialzellen bci den Hi'd>-om?diise>i, by Dr. August 

 Weismann. The first announcement was in Zool. Anzeig. No. 75, 1SS0. 



