1909.] ox THE ROBBER CRAB (bIRGUS LATRo). 887 



based on his original observations, illustrating the life-cycle of 

 the Protozoon, Mmeria {Coccldium) avium Silvestrini and Rivolta, 

 — also known as Coccidium tenellum Railliet and Liicet — a Sporo- 

 zobn parasitic in the alimentary canal of Grouse. The parasite 

 produces a fatal intestinal coccidiosis in Grouse chicks, especially 

 during the first month or six weeks of their life. The immediate 

 effect of coccidiosis in Grouse chicks is enteritis accompanied by 

 diarrhea, and a similar disease in Fowl chicks is known among 

 poultiy-men as "white diarrhoea" or "white scour." 



The life-history of a Coccidium may be divided into two cycles : 

 (u) asexual multiplication, or schizogony, for the purpose of 

 increasing the numbers of the parasite within the host, (/3) sexual 

 reproduction, or sporogony, for the purpose of infecting fresh 

 hosts by means of i-esistant spores adapted for extra-corporeal 

 existence Schizogony and sporogony occur in both the duodenum 

 and caecum of the Grouse chicks, causing great destruction of the 

 epithelium of the gut. The merozoites, or daughter parasites 

 produced during schizogony, are aiTanged " en barillet," like the 

 segments of an orange, within the epithelial cells. A thin cyst 

 wall is secreted precociously around tlie oval macrogamete ( $ ) 

 while still within the epithelial cell, leaving a micropyle for the 

 entry of the microgamete ( S ) later. 



The caica of Grouse chicks dying from coccidiosis are full 

 of oval spores (oocysts), which are passed out with the cajcal 

 droppings, forming a source of infection on the moors. Each 

 oocyst gradually develops four sporocysts within itself, while still 

 in the cascal droppings, and each sporocyst ultimately contains tw^o 

 sporozoites. On the ingestion of the spores by other Grouse, the 

 sporozoites are liberated by the action of the pancreatic juice of 

 the new host, and proceed to penetrate the epithelium of its 

 gut- wall. 



Larvfe of Scatophaga, found in Grouse-droppings, swallow the 

 Coccidian spores and void them uninjured, thus aiding in the 

 dissemination of the spores in nature. Coccidian spores are very 

 resistant to varying conditions of weather and, being light, are 

 easily blown about by the wind, so that the moors are being 

 constantly contaminated during an epizootic of coccidiosis. 



The coccidiosis of Grouse is transmissible directly to young 

 fowls and young pigeons by feeding these birds on food mixed 

 with fa3ces of infected Grouse. Adult Grouse are much less 

 susceptible to coccidiosis than immature birds. 



Dr. C. W. Andrews, F.R.S., F.Z.S., exhibited an enlarged 

 photograph (PI. LXXXIII.) of the Robber Crab {Birgus latro) 

 on Christmas Island, and communicated the following account of 

 its habits : — 



It is somewhat remarkable that althougli the Robber or Coco- 

 nut Crab [Birgus latro) has been known for some centuries and 



