96 NATURAL SCIENCE. August, 1895. 



Pelagic Hemiptera (p. 60, second line from bottom), the word 

 " Italian " was misplaced. It refers to the Expedition and not to 

 the species. 



Of the many kind letters that we have received, we will only 

 quote the following : — " Mr. Gladstone oflfers his very best thanks to 

 the Editor, for the singularly interesting number of Natural Science 

 which he has been good enough to forward to Hawarden. Jul i, 95." 



We learn that a few people have complained that we did not pay 

 enough attention to the chemical and physical results of the Expedi- 

 tion. Our regular readers will understand that those branches of the 

 subject are outside our usual scope, and were, therefore, only dealt 

 with so far as they seemed to appeal directly to biologists or 

 geologists. Another reason might be found in the fact that their 

 inclusion would have swollen our already enlarged number to a size 

 that would have necessitated the raising of its price. Since, however, 

 there may have been some purchasers of the number who suffered 

 disappointment, we make them the best amends we can by offering 

 them, in the present number, an article on the chemical and physical 

 results of the " Challenger" Expedition, for which we are indebted to 

 the kindness of Mr. Ritchie Scott, who, from his long connection 

 with the " Challenger " Office and from his own special studies, is 

 peculiarly fitted to deal with those questions. 



One correspondent, who thinks that we treated the Hydroidea 

 somewhat scantly, reminds us of "the gigantic Tubularian, by far 

 the largest of all known Hydroid-polypes." He writes further, " The 

 specimens of Idia brought home enabled the structure of this 

 remarkable hydroid to be worked out in a way which would have been 

 impossible with the dried specimens hitherto in the hands of zoologists, 

 and have given occasion to the establishment, not only of a new 

 family, but of an entirely new section of Calyptoblastic Hydroids. 

 The determination of the true and hitherto misunderstood structure of 

 Gramviaria, and the establishment of the remarkable family of the 

 Perisiphonidse, afford sufficient evidence that the work of the 

 " Challenger " in this department was not without results which 

 have, to some extent at least, advanced the progress of Hydroid 

 morphology." 



We thank our kind correspondent, but we must remind the others, 

 doubtless not few, who have found some sections less fully treated 

 than they could have wished, that a summary of so gigantic a work, 

 that is to be both short and interesting, must inevitably have " the 

 defects of its qualities." It cannot mete out strictly proportionate 

 justice to every subdivision of the natural sciences. 



