7S 



HAIlDWICKE'S SCIENCE- GOSSIP. 



[April 1, 1S6S. 



can be set out with the usual gum. All specimens 

 should be put into a setting-frame, or pinned in an 

 open box, and exposed to fresh air for a week or 

 fortnight, though Brachdytra best avoid ruun ing 

 up by being first left for a day or so in a closed 

 box. Einally, benzine must be kept to clean 

 specimens from grease, and carbolic acid to destroy 

 mould. 



PHANTOM LARVAE.- 

 By Dr. Carrington. 



EARLY in September, 1S67, while netting for 

 microscopic objects in a favourite pond of 

 mine on the Ellesmere estate, near Eccles, I met 

 with a number of larva? which were new to me. 

 At first I thought I had captured the rare Cheiro- 

 cephalus diaphanus, but on closer inspection it was 

 evident they were the larva? of some dipterous insect 

 (Corethm plumiconiis), and until their true name 

 was obtained, they were generally spoken of by us 

 as the Phantom Larvae. 



* I was ignorant until after the completion of my paper 

 that the subject had been preoccupied by such competent 

 observers as Mr. E. Ray Lankester (Popular Science Review, 

 1865), and Prof. Rymer Jones (Microscopical Journal, Oct., 

 1867). 



Prof. Jones contents himself with a brief but lucid sum- 

 mary of the chief points of interest in the development of the 

 "glass" larva. More fortunate than myself, he has been 

 enabled to describe the wonderful growth of the respiratory 

 system which takes place during the transition to the pupa 

 state. Some of my larva? are still living after three months' 

 confinement (Feb. 10, 1868), but I have watched in vain for 

 their metamorphosis. 



From some points of the professor's description I must 

 dissent. Thus, referring to what I have caUed the antennas 

 (fig. 5, a), he writes : " In their disposition they remind us of 

 the foot-jaws of the Branchiopod Crustaceans (such as Cheiro- 

 cephalus), and in like manner are equally instruments of pro- 

 gression and weapons for the capture of prey. The anterior 

 pair, articulated to the apex of the snout, are of great strength, 

 and are moved by powerful muscles, distinctly seen through 

 the transparent covering of the head. At their extremities they 

 bear fan-like tufts of stiff setae, that, when expanded, form 

 powerful oars, the downward strokes of which, when ener- 

 getically made, have a marked effect in aiding the progress of 

 the animal through the water. More frequently, however, 

 their movements are of a gentler character, and only serve 

 to cause the influx of a constant stream towards the mouth." 



Again, he writes : " The second pair of appendages are com- 

 posed of numerous narrow laminae, much resembling in their 

 arrangement the plates of whalebone in a whale's mouth : 

 and, indeed, they perform a very similar office," for they " can 

 be spread out like the walls of a tent, so as to enclose as in 

 a net whatever small animals may be brought within their 

 expanse by the intrait current above alluded to." Now it 

 must be admitted the uses and homologies of the oral ap- 

 pendages are most puzzling, but I cannot but suppose, when 

 the above words were written, the professor was trying to 

 reason out the problem on the dead animal rather than the 

 living one, or has mistaken the convulsed motions preceding 

 death for normal acts. How can naturalists expect other 

 than lying responses from creatures undergoing the torture 

 of the compressorium, or sealed up alive in a glass cell? 

 After repeated examinations, I have failed to trace any cur- 

 rent, constant or otherwise, towards the mouth referrible to 



My acquaintance with entomology is scanty, ex- 

 tending only to dissections of some few genera; but 

 it was impossible to watch these larva? day after 

 day, and gradually become acquainted with their 

 anomalous structure and strange habits, and not 

 wish others should share the pleasure. I have 

 accordingly made some drawings which at least 

 may claim the merit of accuracy, and shall endeavour, 

 as briefly as possible, to describe those anatomical 

 details which appear to me of most interest. 



The characteristics that would strike an observer 

 viewing them for the first time with an ordinary 

 lens are, first, their remarkable transparency; in- 

 deed, they are so translucent, that unless you know 

 what to look for, it is difficult to make them out in 

 the water. Their specific gravity also coincides 

 with that of water, so that they are enabled to float 

 near the surface, or bottom of the vessel, with- 

 out apparent effort. They differ from all larva? 

 with which I am acquainted by this habit of re- 

 maining suspended in mid-water; seldom seeking 

 the surface for purposes of respiration, as in the 

 case of other Diptera. I must not, however, allow 

 you to form the impression that their habits are 

 sluggish and inert. Ear from this, their quietude is 

 that of the eagle, for, like that bird, they are watch- 

 ful, and ready to pounce in a moment on any object 

 moving beneath them. Their spectral appearance, 

 and the mysterious manner in which they vanish and 

 reappear in unexpected places, will explain the 

 name we ventured to apply to them. One habit 

 seemed at first especially " uncanny," the sudden 

 way in which they make a half-turn, like the needle 

 of a magnet ; so that if we are examining the 

 head, we find the tail substituted in its place, and 

 before we have time to make out the details — presto! 

 the head as suddenly reappears ! Our phantoms are, 

 I fear, not as innocent as phantoms should be. We 

 may rather compare them with vampires which suck 

 the life-blood of unwary victims ;— a glance at the 

 cruel armature of the mouth will satisfy you of this 

 fact. I do not allude to the formidable-looking organs 

 which articulate with the snout, and 'look like the 

 fangs of a viper ; these are modified antenna?, and 

 serve the animal to rake up the surface mud in 

 search of prey. Eoot-like antenna? are also found in 

 some Entomostraca {Candonia), and in Corophia,ii 



the antenna;; nor have I seen them used as oars during 

 progression. The ordinary movements of the larva seem to 

 be due entirely to the anal fan. Each antenna bears four 

 (not six, as in the drawing, Mic. Journ., Vol. xv., PI. ix. f. 3) 

 slender seta; (not plumed, as in true swimming feet), which 

 are used only in retaining the prey, or forcing it upon the 

 lancets, or in raking up the surface mud. The second pair of 

 appendages, again (fig. 5, J), seem to me to be true lancets, 

 and I feel certain I have seen them so applied in piercing the 

 larger Entomostraca, which are then passed on to the 

 powerful jaws. 



In the same plate, the fourth appendage (/. c, figs. 3, 4), 

 which seems to me to be single and trowel-shaped, forming an 

 upper lip, is figured with two blades. 



