PEROPHORA ANNECTENS. 43 



dition here shown is quite characteristic. At the extreme 

 edge of the colony there is a narrow, irregular belt of the 

 testicular mass, in which onh' the stolonic vessels with 

 their numerous short, knob-like branches, their anasto- 

 mosings, and young zooids are seen. This is -par excel- 

 lence the growing region of the colony. One rarely, if 

 ever, lands young buds in other than this marginal zone, 

 though in some cases they are found in what might be 

 called the proximal portion of the colony, where there 

 are long stretches of stolonic vessels bearing few zooids. 

 The region in w^hich the isolated zooids are shown in hg. 

 2 is one of this kind, and some of these are not fully de- 

 veloped. Why few or no zooids are present in these re- 

 gions I am not sure, but think it possible that they have 

 died and fallen away. It will be seen in fig. 4, pi. i, that the 

 vessels do not extend into the test which is situated around 

 and between the zooids: they are confined, for the most 

 part, to the layer that forms the contact with the substratum 

 of the colony. Their branching is mostly in a plane par- 

 allel to the surface on which the colony rests. This latter 

 condition is well shown by the section represented in fig. 7, 

 pi. i. A section of a portion of the testicular mass in w^hich 

 zooids are present, but vessels are not, is shown in fig. 5, 

 pi. i. In some cases, the partition of test that separates two 

 zooids is exceedingly thin, while in other cases it is of 

 considerable thickness. In certain colonies, the zooids are 

 so closely crowded together that they appear on cursory 

 examination to have a common test; more careful inspec- 

 tion, however, discovers that this is not so ; that the test is 

 not continuous from zooid to zooid ; they are only in con- 

 tact with one another. This having been found to be the 

 case in some colonies, it seemed quite possible that in other 

 cases, where the test appeared to be a unit for the whole 

 colony; where the zooids could not be separated by me- 



