HARDWICKE'S SCIENCE-GOSSIP. 



203 



haunt : this was clearly seen by the great scarcity of 

 Crustacea, The arrival of the cuttle is the signal for 

 the departure or death of a host of things, but 

 especially of Crustacea, small heaps of the shells of 

 which testify to their rapacious appetite ; nor are 

 mollusca free from their embrace, although they are 

 not so easily made a prey as crustaceans. We only 

 found a couple of this cephalopod. I was much 

 amused on turning over a large stone to see a pair 

 of remarkably bright eyes staring at me, and to see 

 eight leathery arms scraping together stones and 

 shells, in order to screen the creature from 

 observation ; however I picked him up and trans- 

 ferred him to my fish basket, and, in doing so, 

 experienced the curious sensation caused by the 

 suckers of the skin. Being a somewliat young one 

 and out of water, his hold was very slight, but, having 

 experimented with a large one on a former occasion, 

 I am inclined to think that their power is somewhat 

 overrated. But to return to our captive, who by 

 the way is now before ma in a large jar of spirit. 

 Whenever I opened the basket he commenced 

 swarming over the side most quickly, and I nearly 

 lost him more than once. Their mode of progression, 

 by means of their arms, out of the water, is by no 

 means slow. Of Crustacea we did but little in the 

 way of collecting, for reasons already given, the only 

 species I observed being Cancer paguriu, Carcinus 

 mcenas, Maia sqtdttado, Porcellana platychelcs and 

 P. hngicornis, Palanion squilla, a few of the 

 Hippolytes, and perhaps one or two others ; in fact 

 a very poor series indeed for a spot usually so rich. 

 But a few days later, after it had been blowing a bit, 

 I found at high-water mark several dead specimens 

 of Pirimela denticulata, a very uncommon and pretty 

 crustacean. 



Unfortunately a tide is not long enough to do 

 much work, and it is very seldom anyone is able to 

 penetrate so far as we did on this occasion, besides 

 the fact of its being unpleasant to be five miles from 

 high-water mark with the tide flowing. 



Again, no dredge could possibly work for five 

 minutes amongst such a tangle of outcropping rocks, 

 with gullies and stretches of sand between, so it will 

 be understood why I believe it almost impossible to 

 arrive at anything more than a scanty knowledge of 

 the Fauna of the coasts of an island so close to us as 

 Jersey. 



The Fitzroy weather-glass is composed, I believe, 

 roughly speaking, of spirits of wine, camphor, water, 

 &c., and is enclosed in a glass bottle which is hermeti- 

 cally sealed (or not). But in the former case, how 

 can the atmosphere act on the contents of the bottle, 

 which is reputed to cloud and clear for wet and fine 

 respectively ? I have never heard this conclusively 

 answered. — L. G. F. 



THE ORGANS OF RESPIRATION AND CIR- 

 CULATION IN THE COCKROACH.* 



By Professor L. C. Miall and Alfred Denny. 



THE respiratory organs of insects consist of 

 ramified tracheal tubes, which communicate 

 with the external air by stigmata or spiracles. Of 

 these spiracles the cockroach has ten pairs ; eight 

 in the abdomen, and two in the thorax. The first 

 thoracic spiracle lies in front of the mesothorax, 

 beneath the edge of the tergum ; the second is 

 similarly pkaced in front' of the metathorax. The 

 eight abdominal spiracles belong to the first eight 

 somites ; each 'Yits in the fore part of its segment, 

 and hence, apparently, in the interspace between two 

 terga and two sterna ; the first abdominal spiracle is 

 distinctly dorsal in position. 



The disposition of the spiracles observed in the 

 cockroach is common in insects, and, of all the 

 recorded arrangements, this approaches nearest to 

 the plan of the primitive respiratory system of 

 Tracheata, in which there may be supposed to be as 

 many spiracles as somites. The head never carries 

 spiracles, except in Smynthurus, one of the Collem- 

 bola (Lubbock). Many larva; possess only the first 

 of the three possible thoracic spiracles ; in perfect 

 insects this is rarely or never met with (Pulicidse?), 

 but either the second, or both the second and third 

 are commonly developed. Of the abdominal somites, 

 only the first eight ever bear spiracles, and these 

 may be reduced in burrowing or aquatic larvae to one 

 pair (the eighth), while all disappear in the aquatic 

 larva of Ephemera. 



From the spiracles short, wide air-tubes pass 

 inwards, and break up into branches, which supply 

 the walls of the body and all the viscera. Dorsal 

 branches ascend towards the heart in the intervals 

 between the alary muscles ; each bifurcates above, 

 and its divisions join those of the preceding and 

 succeeding segments, thus forming loops or arches. 

 The principal ventral branches take a transverse 

 direction, and are usually connected by large 

 longitudinal trunks, which pass along the sides of the 

 body ; the cockroach, in addition to these, possesses 

 smaller longitudinal vessels, which lie close to the 

 middle line, on either side of the nerve-cord.f The 

 ultimate branches form an intricate network of 

 extremely delicate tubes, which penetrates or overlies 

 every tissue. 



The accompanying figures sufficiently explain the 

 cliief features of the tracheal system of the cockroach, 

 so far as it can be explored by simple dissection. 

 Leaving them to tell their own tale, we shall pass on 



* For the natural history, the outer skeleton, and the alimen- 

 tary canal of the cockroach, see this Journal, March, May, and 

 July, 1884. 



t The longitudinal air-tubes are characteristic of the more 

 specialised Tracheata. In Araneidas, many Julidae, and Perl- 

 patus, each spiracle has a separate tracheal system of its own. 



