356 SUMMARY OF CURRENT RESEARCHES RELATING TO 



only, it might be expected to persist to the mature Btate in all 

 glochidia. 



Lefevre and Curtis discovered metamorphosis without parasitism in 

 Strophitus edentulus. Howard notes that infections have not been 

 found for Obliquaria reflexa and Anodonta imbecillis, and that in the 

 latter the young mussels lie crowded in the marsupial gills of the parent 

 without any conglutinate structure or placenta. The glochidia taken 

 from Anodonta imbecillis did not at first respond to the presence of 

 fishes, but in a postscript the author states that he has been able to 

 secure infections and encystment on fishes with A. imbecillis and with 

 Strophitus edentulus. In the latter complete metamorphosis was observed, 

 but metamorphosis on fishes was not secured for A. imbecillis. There 

 seems no doubt that this species, already eccentric in being hermaphrodite, 

 has a development without parasitism. 



Hosts of Glochidia.* — A. D. Howard calls attention to cases in 

 which the glochidia are restricted in their parasitism to particular 

 fishes, e.g. the Warty-Back Mussel to the catfish. The Mucket (Lampsilis 

 ligamentina) and Lake Mucket {L. luteola) have an extensive range of 

 parasitism on several genera of fishes, while the Yellow Sand Shell 

 (L. anodontoides), a closely-related species, is parasitic upon a single 

 genus of fishes (the Short-nosed Gar, Lepisosteus platosomus) far re- 

 moved from the others. Any of the three species {L. osseus, L. plato- 

 stomus, and L. tristoechus) seems to be a suitable carrier for the mussel 

 in question. The glochidia of Obovaria ellipsis remained and passed 

 through the parasitic stage on the sturgeon {Scaphirhynchus plato- 

 rhync/ius), while they were promptly shed by the black bass, sunfish 

 {Lepomis pallidus), sheepshead (Aplodinotus grunniens), and so on. The 

 butterfly shell {Plagiola securis), P. donaciformis, and a third species, 

 are confined chiefly to one host — the sheepshead. 



Arthropoda. 

 a. Insecta. 



Clasping Organs of Insects. f — G. T. Bethune-Baker discusses the 

 more or less external armature at the telum of insects. There are no 

 clasping organs in Thysanura and Collembola, only certain stylets and 

 sensory gonapophyses. In Orthoptera there is a combination of primi- 

 tive and progressive characters ; the cerci are strongly developed, whilst 

 the clasping organs are present, but probably are not strong enough to be 

 of much use. The Thysanoptera seem to have genital characters some- 

 what like those in Thysanura, confined to sensory gonapophyses and 

 stylets. The clasping organs seem to be modifications of the ninth and 

 tenth abdominal segments. In Lepidoptera, Trichoptera, and Diptera, 

 they are very ancient structures. The Coleoptera do' not seem to have 

 true homologues of the Lepidopterous external organs. The same 

 applies to the Hymenoptera. The Odonata are cjuite by themselves 



* Trans. Artier. Fisheries Soc, December 1914. pp. 41-4. 



t Trans. Entomol. Soc. London, 1914, pp. cxix-clxviii (19 pis.). 



