EFFECTS ON THE HIGHER INVERTEBRATES 33 



through alternate periods of fasting and refeeding. Underfed larvae of the 

 moths Acronyeta and Bombyx produce smaller pupae and adults, the effect in 

 the case of Bombyx being often carried over to the second and third generations. 



Effects on the Various Phyla 



Among the metazoan invertebrates, the effects of inanition upon growth and 

 structure have been studied most extensively in the phyla Coelenterata, 

 Platyhelminthes and Arthropoda. Some investigations, however, have been 

 made also upon the Porifera, Nemathelminthes, Trochelminthes, Echinodermata, 

 Annulata, and Mollusca. A few observations upon the Urochorda (Tunicata) 

 are also included. 



PORIFERA 



The effects of inanition upon sponges have been studied chiefly by Maas. 

 His first work ('04, '04a) was on the effects of a partial inanition upon the 

 development of Sycandra setosa in CaC0 3 -free sea- water. "Die Larven.im 

 kiinstlichen, karbonatfreiem Seewasser machten ebenfalls ihre Metamorphose 

 durch, indem sie ungefahr in der gleichen Zeit festsetzten und ihre dermalen 

 Zellen nach aussen, die gastralen nach innen kehrten; sie zeigten aber nach 24 

 Stunden und noch spater keine Spur von Nadeln oder sonstigen Kalkkonkre- 

 menten." The skeleton is normally formed if the CaC0 3 is merely reduced in 

 amount, but CaSCu cannot be substituted. In the CaC03-free sea-water, the 

 body form is abnormally flattened, and various developmental irregularities 

 occur. Usually the cells finally spread out into a flattened mass, which ulti- 

 mately disintegrates. 



In 1906, similar experiments by Maas on Sycandra raphamis were extended 

 to include various larval and adult stages. When placed in artificial sea-water 

 without CaC0 3 , larval metamorphosis occurs. "Es kommt zum Ansetzen, 

 zur sog. Umkehr der Schichten, Kalknadeln werden nicht gebildet; trotzdem 

 zeigt sich ein Hohlraum, ja mitunter auch ein Osculum." These organisms 

 without skeleton soon collapse unless CaC0 3 is supplied, in which case they may 

 recover normal structure if the cells have not been too greatly injured. 



When place in entirely Ca-free solutions (both carbonate and sulphate absent), 

 the development is arrested earlier, in the amphiblastula stage. The ciliary 

 mechanism is unaffected. On the fifth day, the granular ectoderm cells of the 

 posterior half of the body become loosened and detached. The anterior mass 

 of ciliated entoderm cells may persist for a week. Upon replacing the larvae 

 in normal sea-water, recovery of more or less normal structure is possible, unless 

 the granular ectoderm cells have been lost previously. 



When the larvae, after normal metamorphosis, are transferred to CaC0 3 - 

 free solution, the previously formed calcareous spicules are gradually dissolved. 

 The gastral cells form a rudimentary cavity and the dermal cells continue differ- 

 entiation, but development gradually ceases in a variable time. In totally Ca- 

 free solution (containing only Na and Mg salts) the skeletal spicules begin to 

 disappear in a few hours. In one day, the soft parts also are degenerating ; dermal 



