Sea- spiders. 177 



the ova, the flow continuing for about fifteen minutes, 

 and, to all appearance, in two streams, this being 

 one among the numerous instances above referred to 

 of the astounding powers of multiplication in marine 

 animals. 



Besides the crab and the worms, Mr. Robertson 

 took from among the fibres of the nest of this same 

 mollusk a rare species of isopod, which Bate and 

 Westwood named Munna Whiteana. It is not 

 perhaps very remarkable that, when a nest or home 

 is constructed by one animal, other creatures should 

 take advantage of the ingenuity and labour employed, 

 but it is scarcely a piece of common knowledge that 

 even a shell-fish can build itself a house, and adapt a 

 variety of materials to its purpose. 



Mr. Robertson was corresponding at this period 

 with nearly all the men of eminence whose writings 

 were concerned with the treasures of the sea. In 

 1863, we find him sending a nudibranch to Mr. 

 Joshua Alder, of Newcastle ; and in the same year he 

 opens an intercourse with Mr. G. S. Hodge, known 

 for his investigation of the pycnogonida, a kind of 

 sea-spiders, so slender in body that the digestive 

 cavity has to be prolonged into the legs. Now, too, 

 he becomes acquainted with Dr. G. S. Brady, with 

 whom, not long after, he was to make scientific 

 expeditions and write elaborate scientific papers. In 

 the following year he began to correspond with Mr. 

 Henry Brady on the foraminifera, in the study of 

 which it has been already mentioned that Mrs. 

 Robertson has taken an exceptional interest 



In 1865, Dr. Baird, of the British Museum, published 



N 



